The Fitbit Sense: A Review

The SpO2 watchface of my new Fitbit Sense

John ScalziI’ve been using Fitbits for a couple of years, first to help with my weight loss and exercise regimen, and these days to help maintain my current weight and otherwise keep on top of my health (in a very general, this-is-not-an-actual-medical-device way). Fitbit recently announced a new top of the line model, the Fitbit Sense, and I was looking to upgrade, so I went ahead and got it.

I’ve had it now for a couple of weeks and I’m pretty happy with it, although frankly I’m not entirely sure that many of the new bells and whistles are things I need, or track things I need to be especially concerned about. For example, the Sense tracks my blood oxygen levels (you can see the blood oxygen tracking watchface above, which apparently is the only watchface that you can use if you want the watch to track blood oxygen levels, although why that would be the case is a little puzzling to me). While it’s nice to know that for the last two weeks I’m at a more or less consistent 96% blood oxygen saturation level, I’m not entirely sure what that means, how it matters or why, outside of a COVID-19-like situation, I need to care very much. I’m sure someone can and will explain in the comments why this is important, but at the moment, it’s just, huh, I guess I’m getting enough oxygen.

This goes for other features, like trackers for my skin temperature, heart rate variability and breathing rate, all of which are tracked whilst I sleep (the Sense also tracks how much and how well I am sleeping). I think all of these features are probably useful for someone; I’m not sure that person is me. To be sure, I think it’s fun to know my skin temperature last night was a degree less than it usually is (I had a leg out of the blanket for most of the night), but again, so what? For me it’s just kind of random data, and not data that is exact enough necessarily to be of medical use (again, the Fitbit people make pains to note the Sense isn’t strictly a medical device). I’m sure all this information is in the ball park; I’m just again not sure why I should care.

The feature that sort encapsulates the Sense’s “sure it’s cool, but also, so what” suite of features for me is the EDA scan, which is supposed to trace “electrodermal activity” on your skin to give you an idea of how stressed you are. You start up the app on the phone, put your hand on the watchface (covering the metal band that goes around the watchface), and then you bliss out for a couple of minutes while the watch senses how many electrical twitches you have in your hand (I’m, uh, paraphrasing here), which apparently correlates to your stress levels.

Does it? I mean, maaaaybe? The first time I did I felt pretty relaxed and it told me I had had 11 EDA events in two minutes, which seems like a lot. The next time I did it, I got zero EDA events (which is supposed to be good!), although I personally didn’t feel any more relaxed and indeed had just got done reading news about our damn fool president doing some damn fool thing. As other people have noted, taking a couple of minutes just to be still and bliss out isn’t a bad thing; I like taking the EDA test just to have a moment to do nothing. But I don’t know how accurate the test is as it relates to my actual stress levels (likewise the numerical value it attaches to my overall Stress Management level). I feel more than vaguely that it’s probably a bit of “we’re making things up to have something to sell” here.

Not that I’m accusing Fitbit of any particular nefariousness, or at least, if they are engaging in nefariousness, then so is every other smartwatch manufacturer out there, including Apple and Samsung, since all the smartwatches these days have more or less the same suite of health and wellness trackers. We want to be able to quantify how we’re doing and feeling, and they want to sell smartwatches, so in the end everyone is happy, I suppose.

And in point of fact I am happy — like I said, having all this information at my fingertips is fun and interesting and maybe once I figure all of it out, who knows, it might even be useful. For now, though, it seems mostly frippery designed to make me feel like I’m doing something for my health and to justify the $330 price point.

It turns out I’m primarily still using the Sense for what I used my very first Fitbit for, and every one since — tracking steps and heart rate, and also, using the Fitbit app and Web site to jot down my calorie consumption over the course of a day. And for that, the Sense, like all the other Fitbit appliances I’ve used, does a pretty good job! It’s why I keep getting the company’s products.

Because the Sense is Fitbit’s top of the line product, it also has some other nice bells and whistles, including an improved screen, GPS in the watch itself, and a limited but nice number of apps one can use from the watch, including Spotify and an NFC payment option, as well as the option to get phone messages and other alerts on one’s phone. I personally use almost none of these — I turn off nearly all notifications on my phone as it is — but because I’m a tech dweeb who geeks out at multifunction, I like that I have the option of all this stuff I don’t use.

Oh, and it tells time just fine.

Two very specific things I can criticize the Sense for: One, Fitbit did away with the physical side button for a “haptic” button, which would be fine if that button worked reliably, but it doesn’t, so it’s just annoying and largely not useful (you can also tap the screen to wake the watch up and scroll about, but I’d prefer having an actual button). Don’t replace things if what you’re replacing it with doesn’t work as well. Two, there’s a bit of a time lag when one scrolls through for apps and information, which is not great, considering this is the top-of-the-line Fitbit.

(Oh, and — I’m currently using the Fitbit Premium service, as the Sense comes with a six-month trial. It offers a bunch of workout and fitness stuff and apparently I can even chat with a Fitbit expert to tailor a workout regimen if I want. I can already tell this is more than I will ever use and will probably drop it before I get charged $10 a month for it. But if this is the sort of thing you think is useful, then, hey, it’s cheaper than Peloton, I suppose?)

I like my Fitbit Sense and I’m happy with my purchase. It does all the things I want it to do very well, has a bunch of functionality which might be useful for me if I can ever figure why I should care about it, and otherwise has a feature set I’m not gonna use but in the abstract enjoy that I have the option for. It looks good and I think it’s worth considering if you’re not already hopelessly tied into the Apple watch ecosystem or otherwise have another smartwatch family you’ve pledged your troth to. I do think people should look to see if they need all the functionality the Sense offers, since Fitbit has several other options (including the newly released Versa 3) that cost less and do the core functions of Fitbit just as well, and offer the same access to the Fitbit app and site. If what you really want is just steps and heart tracking, there are other ways to get that done, without the hit to your credit card.

But if you want all the smartwatch things, then sure, give the Sense a look. It’ll give them to you, whether you need them or not.

— JS

29 Comments on “The Fitbit Sense: A Review”

  1. I mean, the oxygen levels dipping can be an early sign of COVID, before other symptoms crop up. And there is some evidence that the way it affects people can leave them not feeling short of breath even if their oxygen levels are low. That said, I don’t think it’s something most people need, but if you’re in a position where you have to potentially be exposed to COVID on a regular basis (front line workers, etc.), it couldn’t hurt.

  2. In addition to blood oxygen levels, heart rate irregularities and an increase in body temperature (skin temperature readings are an imperfect proxy for that, but continuous monitoring can tell you something) can also be warning signs for COVID. Looks like a lot of the new features are catering to people’s concerns about that.

  3. And does Fitbit promise not to sell your health history to your insurance company? I mean no worries now, but if SocialistCare gets cut off by the Reichpublicans, Fitbit records could be a useful way for your next potential insurer to complain that you like about a preexisting condition. I know, not likely a worry for you personally, but …. just wondering about voluntarily attaching a tracking device.

  4. Oh, PS — does the blood oxygen level give you a “CHECK OIL” warning if the reading goes below 90? I ask seeing that the device face specifies 90-99 percent as the display range, but I read that “Values under 90 percent are considered low” https://www.mayoclinic.org/symptoms/hypoxemia/basics/definition/sym-20050930 so wondering what it tells you.

    I have one of those PulseOximeters cheap from China (used to cost under $10, now around $30) bought for hang gliding use, and it will display below 90 though I have no idea how low it can go.

  5. You’re welcome.

    (I bought a Versa 2 about a week before they announced the Versa 3 and Sense, which have features I definitely would have waited for if I’d known, like built-in GPS.)

    Worth noting if you’re buying a Fitbit device: Google is in the process of buying them and the purchase looks likely to go through at this point. Whether this is a plus or a minus is a personal judgement call, but it’s something to keep in mind.

  6. I think the heartrate variability, etc. are mostly useful as a trendline. I have a whoop and it claims to be able to tell me when I need to take a rest day vs. being able to go harder in a cardiovascular sense. It might be useful when travel and cons start up again? Like it might tell you to take it easy the day after a bunch of traveling or give you a sense of what activities help you recover?

  7. My sense is that the blood O2 takes a lot of power (relatively speaking, these devices all take tiny amounts of power) and requires a larger battery and larger form factor. I personally don’t find it all that useful — my thinking is that if I feel ill, I can take a O2 reading with a fingertip device — but for those who want that functionality, it is truly amazing that it exists.

  8. Not a Fitbit user, but was glad last week that I’d bought an oximeter and forehead thermometer recently. Developed some lung and sinus congestion a week ago, with headache as well. Oximeter showed 90 instead of my baseline 95, which was concerning.

    But I began checking oxygen and temp every few hours. After that one low reading, numbers went back to normal range by evening, and never exhibited a fever. Without those two bits of tech, the past week would have been a LOT more stressful.

    (Best guess: Combination of seasonal allergies and reacting to dust raised by some long overdue deep housecleaning.)

  9. What things does the Fitbit actually MEASURE, instead of just estimate?

    I’m sure it’s a more-or-less accurate step-counter, since my phone can do that too. Or could, if I took it with me more often. But what else? Skin temperature, probably, Blood pressure, maybe. (Probably badly, because doctors still insist in puting something on your arm that tightens and makes your fingers go numb to do so…

    What else does it actually DO?

    I’m highly sceptical of stuff like the Fitbit, since I believe they can’t actually take accurate measurements of the things it PRETENDS to tell you about. And all the stuff I’m sure it CAN do, my phone can do as well.

    Then again, if you like it… Hey it’s not like you bought it with MY money…

  10. Proceeding on a more focused basis, I suggest that you spend a few dollars on a Sats monitor; you stick it on one of your fingers and it tells you what your sats are. The only thing that I need to do is to remember to change the batteries every so often, to prevent my daughter harassing me.

    She is a consultant physician in an Acute Medical Unit, and would, I have no doubt, wish me to point out that there are a lot of things which are not Covid 19 may still result in your Sats being lousy, which, if not treated, could result in your death/lifelong disability etc. so please do not overlook that.

    She carries one everywhere, and does not own a Fitbit. I suppose that when you are at the sharp end you cut it down to the essentials. And should you, John, be unfortunately carted off to hospital then nobody is going to be interested in the data in your Fitbit. They haven’t the time to dredge through stuff; they have a potentially dying patient on their hands and what matters is making the diagnosis so they can begin treatment. I’m sure the Fitbit is fun but if you are using it because you think it’s going to save your life then please don’t…

  11. Take it for what you will, but the President’s doctors saw his O2 sat drop to 93, and they casually rushed him to the hospital as soon as the stock markets had closed.

    My experience with Pulse Oximeters has been with my parents who both had COPD. And also with myself about 18 years ago when I was hospitalized for a DVT/PE. If you spend a lot of time on airplanes, or a lot of time sitting, such as in front of a computer when you’re on a deadline, you could be susceptible to DVT.

    In short, I think having a pulse oximeter becomes more useful as you get old (and want to get older).

    I wear an Apple Watch, and the latest version has that feature. I’m not rushing to upgrade, as I have last year’s model, but I’m happy to know the feature will be available on the model I get when it is time to replace my current Watch.

    And a pulse ox that is in the device you wear every day is more useful than one in a drawer with questionable batteries.

  12. That EDA sounds like one of the things the polygraph measures to see if you’re stressed. I don’t know anyone who’s been polygraphed who believes it measures anything useful. It’s a truly absurd experience.

  13. I use my FitBit (charge 2) for tracking sleep, mainly. I also find the heart rate monitor and step/ activity counters interesting.

    But I think it’s important to try not to be reliant on it – I read something a couple of years ago that suggested that an over-reliance on fitness trackers can be a sign of other problems regarding food and exercise. E.g. how some people would pace around their bedroom before bed, just so they get the so-called “right” number of steps.

  14. Back when I was on Fitbit, I always wished I could add you, as someone to go up against. But those days are gone now, I switched to Apple for the heart monitor.

  15. Low oxygen levels are in some cases the only sign of serious COVID-19 problems. It is called silent hypoxia and there is a reason it is called “silent.”
    Early on I got a fingertip oximeter (which also shows pulse rate). Not the most accurate measurement (supposed to be within 2% of the true figure) but it will do.

    I would keep an eye on this off and on even if you have no known exposure to the virus. It’s easy to watch and potentially significant.

  16. How is the battery life? That’s my one big driver for smart watches. I’m pretty plugged into the Apple universe these days, so when my second Versa crapped itself I replaced it with an Apple Watch, and the battery life is terrible. I can’t reliably use it for a 24-hour period without shutting off a bunch of the functionality that might be useful AND having a charger close by.

    On the other hand, Fitbit’s refusal to write their data to Apple Health is also a cause for regret. Given I am diabetic and have a meter that *does* write directly to Apple Health, that’s a useful place to consolidate my data and I have a little more trust that Apple will not sell my data, and that it will fight to keep from releasing it, than I do for most other tech giants these days.

  17. Kevin

    My daughter doesn’t leave her oxygen Sats monitor in a drawer, and neither do I; I have this predilection for staying alive. Strange, I know, but if you, like me, regard a year with only a couple of hospital admissions as a great result, then perhaps you too would understand why I ignore all the high tech stuff.

    The hospitals have got all the high tech stuff they need; What you need is a simple device which demonstrates that the hospital does need to take you, and your Sats, really seriously. And since early diagnosis definitely helps you to survive longer in almost all disease it’s probably sensible to check on it yourself a couple of times a day. That way my daughter has a greater chance of not having to try to resuscitate you when you arrive at her hospital, and everyone is happy…

  18. GPS? or micro-GPS? can your wife track your movements to the nearest meter? centimeter?

    Q: can it weigh you before-after frig trip? can it detect how many slices of pizza (or scoops of ice cream) you’ve sneaked?

    Q: what’s monthly fee for it not to rat you out to your wife whenever you midnight raid the frig for slice of cold pizza?

    …asking for a friend

  19. This sounds like it might be closer to what I’ve been looking for, as far as combining the functions of a top-tier Fitbit with those of a Galaxy Watch. But based on the Amazon reviews (and the price, egads), I’m going to hold off on possibly buying one while they hopefully work out the kinks.

  20. So, besides the aforementioned use for detecting severe COVID-19 symptoms, it is also unfortunately true that many, many people have COPD – Chronic Obstructive Pulmonary Disease, which is what smokers (and people in developing countries that use propane cookstoves) get after years of exposure. Unlucky smokers get lung cancer, “lucky” smokers get COPD and carry around oxygen with them wherever they go for the rest of their lives. But sometimes they try not to have to use the oxygen all the time, and they also try to moderately exercise. a Fitbit Sense (if they can afford it), could give them and their loved ones a lot of peace of mind. Similar is likely true for folks with frequent sever asthma.

    The heart rate thing could be helpful for people with cardiac symptoms, and/or people with pacemakers, for similar reasons.

    Pretty sure you do not yet fall into any of these groups, which is why these features aren’t super helpful to you right now.

  21. I just upgraded to a Charge 4 when my Charge 2 battery started running down more frequently and the strap broke. I picked the Charge 4 for the GPS, but have been unable to find the right combo of settings to make the GPS work, and so am still using the GPS on my phone to track my neighborhood walks. Also, the Charge 4 vibrates annoyingly at seemingly random times, no matter how many places in settings I’ve turned off “vibrate”.

    Both the sleep and heart rate tracking on the Charge 2 were useful and reasonably accurate (I compared the latter with pulse rate at doctors appointments). And those were the specific reasons I first bought a fitness watch.

  22. SpO2 is of vital importance to anyone with sleep apnea. It will definitely be useful for people using therapy for apnea to confirm it’s keeping their oxygen levels up, and be a sign their therapy might need adjustment if it doesn’t. Anyone who has consistently low spO2 would probably be well served to mention it to their doctor – who will in all likelihood advise apnea testing.

    As for temperature variations, I believe that is most likely to be of interest to women, except when a significant spike indicates an oncoming illness. (Side note, I learned from experience that a significant spike in resting heart rate can precede symptoms of the flu by a couple days. Last terrible flu I had, my resting heartrate went up by about 8bpm in the several days before I started showing symptoms. I watch that more carefully now.)

  23. Stephanie

    You will be pleased to know that a simple and very cheap Sats monitor is used in Pulmonary Rehab programmes; usually, though not invariably, for people with COPD; not everybody will have COPD – they may, for example, have asthma, – but they can still benefit from the rehab.

  24. thanks for the thread john. this senior’s not paranoid, no sir, but grateful for recommends to keep an oximeter handy at home. look out amaz*n, here i come..

  25. Interesting. –Having a HUGE body of data like this has got to be of some medical use to SOMEbody, in that Big Data sense. Just like all of Tesla’s driving data has got to have some utility.

    Science-fictionally, I’d think every spaceship and space station would require people to have these on, to spot anomalies/health hazards. –Y’know, that Star Trekkian trope of “so-and-so is not on the ship” has always bugged me: you’re a super computer, aren’t you checking where EVERYBODY is every tenth of a second? (Which immediately makes me wonder “and how would Bad People subvert this?”.)

  26. I’m a current fitbit Charge 3 owner and I’ve also been toying with the idea of getting the fitbit Sense. One of my concerns is with it being bigger, will I notice it while I sleep. What are your thoughts?

  27. I’ve still got my ancient FitBit One (the kind that goes in your pocket) and I’m dreading the day it dies because it looks like now everything is a smartwatch or at least intended to be worn on the wrist. I’m very particular about my watches (I’ve had my analog for more than a decade now) and I’d feel like a dork with two watches.

  28. This is one of those “it’s not a medical device, BUT –” stories. I gave my gadget-crazed husband a plain, bare bones FitBit not long after they came out. If I recall correctly, all it did was measure steps, heart rate, and sleep. He’s very data driven and really enjoyed keeping track. He had it about a year when he realized that he was getting a very low resting pulse rate. At first he was sort of pleased – “Hey, I’m in pretty good shape, aren’t I?” – but then he realized that his exercising heart rate never got too high, either. He was concerned enough to take that data to his doc, who referred him to a cardiologist. Two weeks later he was in for a heart ablation – cells in his heart were misfiring, and the FitBit wasn’t able to read the misfires, giving him the low heart rate. Without treatment, the misfires may never have gotten worse, but they could just have easily led to a heart attack. Best present I ever gave him!