Digital health wearables were already big news at CES 2020, but interest has accelerated with the advent of COVID-19 and people's interest in learning whether they might be getting sick. Unfortunately, the pandemic also delayed a lot of the promised devices. Finally, though, they are starting to roll out. But it's an open question about whether they'll really tell you what their makers are hinting they can.
We'll take a look at what's possible with some of the new devices, the issues and drawbacks they still have, and also give you the results of some hands-on testing with Zepp's new E smartwatch ($249 direct) and Amazfit's new Band 5 ($49 at Amazon).What You Can Track
From reading the datasheets and product brochures on the steadily-increasing array of health-oriented fitness wearables, you'd think that they had a few dozen different kinds of sensors. In reality, the actual data collection mostly revolves around just a few. The most common is an optical Heart Rate (HR) sensor. If the sensor and software are good enough, it can be used to also estimate Heart Rate Variability (HRV), pulse-oxygen (SpO2), and VO2 Max.
However, devices have struggled to get accurate enough at any of the above to be truly useful. They typically also can't give you a continuous reading on most of them while you are awake and moving around, as it introduces too much noise into the HR sensor to do the calculations necessary with decent accuracy. With many devices, you can only get a VO2 Max reading if you hike or run, as they rely on GPS plus heart rate. So many sports and workouts won't get you one.
I find that my Fitbit Versa 2 does a good job of automatically detecting exercise and sports, as well as logging and displaying HR and Zones.
Measuring SpO2 Does Not Make a Wearable a Pulse-Oximeter
In theory, though, the devices can make up for some of the difficulties of measuring from your wrist by evaluating you over the course of a night, or if you stay still long enough. However, comparing the overnight SpO2 readings on my Garmin Vivosmart 4 and Fitbit Versa 2 with a medical-grade pulse oximeter doesn't show either of them to be very accurate. Other reviewers have found the same problem with readings from the new Apple Watch 6 and Fitbit Sense.
A really terrible reading would at least be a reason to do more testing or get evaluated for sleep apnea, which is at least a potential benefit. Given all the recent interest in low SpO2 as a possible symptom of COVID-19, though, many device makers have started touting their ability to take daytime readings. This is potentially at best a cause for false alarms, and at worst it raises the possibility of a false sense of security. If you really need to know your SpO2, do yourself a favor and get a real finger-based pulse-oximeter. If you want one you can wear overnight, the one I sometimes use is the Wellue O2Ring ($179 at Amazon(Opens in a new window)).
About all Those COVID-19 Wearable Headlines
Of course, what I said above hasn't stopped health-oriented wearable vendors from charging headlong into the potential market for early detection of COVID-19 (and other diseases, of course). We wrote about the UCSF/Oura study that started this spring, but aside from filling out a questionnaire every day for the past six months, I haven't seen any results. The NBA and WNBA are using the rings (pro golf is using a competing product), but they are deployed in conjunction with a daily symptom survey. Several other large studies that were started for general disease prediction have added COVID-19 detection as a goal. While various device makers have impressive anecdotes about wearers noticing troublesome trends and going to see a doctor, there haven't been any large-scale results reported yet.Pick Your Magic Metric
In addition to the basic health data collected by this latest crop of wearables, each vendor has at least one proprietary metric that it hopes will be helpful in keeping you fit and healthy. Garmin has Body Battery -- a measure of how ready you are for exertion. Oura has a Readiness score -- based on how well your body recovered while you slept. Amazfit/Zepp has PAI -- based on correlating your activity level with your age and other factors to see if you're getting enough exercise.
In my experience, none of those metrics are incredibly consistent, and they often disagree entirely with each other. I can wake up in the morning with a gold crown on my Oura Readiness score telling me up for the challenges of the day while getting a pathetically-low Body Battery reading. Overall, though, both measures do a reasonable job of trying to tell you what you might already know--how you feel when you wake up.
Zepp's PAI takes a different approach. It uses a metric, based on some University research, that tells you whether you are getting enough activity. It worked pretty well on the Zepp E watch and seemed to track nicely with my hikes and sports. But with the Amazfit Band 5, I could exercise for an hour or two and hardly get any credit. It also always seems to be a day behind. However, I do have a pre-release band with early firmware, so hopefully, those issues will be addressed.
Stress level measurement typically starts with HRV, which is tricky to measure with an optical sensor.
Field Testing Huami's New Zepp E Smartwatch and Amazfit Band 5
Amazfit and Zepp aren't well-known brands in the US, but its parent company Huami may make more wearables than any other firm worldwide. Above all else, Huami is known for delivering a lot of features at a low price. Recently Huami restructured the offerings from its two brands, Amazfit and Zepp, unifying their hardware devices on the Zepp software platform. I've been able to test an early version of both Zepp's new smartwatch, the Zepp E, and Amazfit's new band, the Band 5. Both provide sleep tracking, heart-rate monitoring, and a full suite of fitness tracking capabilities.
The first thing you'll notice about both devices is the large, gorgeous screens. The Band makes my Vivosmart 4 look like a toy (in more ways than one, as it is also much larger), and the Zepp E watch is much brighter than my Versa 2. So if you have trouble reading your wearable display in bright light, Zepp may be an appealing option.
The Zepp platform isn't really a full smartwatch-capable ecosystem. It doesn't support many apps out of the box, and you can't add any. So it is best to think of even the Zepp E smartwatch as a high-end fitness tracker with a large display. Given that limitation, in my testing, the Zepp E did an excellent job of tracking my vitals and exercise, similar to that of the Garmin and Fitbit devices I wore on either side of it. However, for the price ($249 direct(Opens in a new window)), a lot of users will miss that it doesn't have either GPS or contactless payment. On the plus side, battery life is amazing, nearly as long as a lot of simpler bands.
Other than having a unified software platform, my experiences with the Zepp E smartwatch and Amazfit Band 5 were very different. In addition to accurate tracking, I found the Zepp E's calculation of Zepp's proprietary PAI (Personal Activity Index) to be helpful in keeping me on track for some combination of walking & structured exercise. In contrast, the Band 5 simply didn't accurately read my heart rate when exercising, so all the resulting metrics were way off. I tried it on various places on my wrist, with and without wearing other trackers, and haven't been able to get it to work well. Now, my unit is a review unit that was shipped out early, so I hope Amazfit can get the issue sorted out, as the device's low price ($49 at Amazon) and bright screen make it a great value given its integrated sleep tracking and other health metrics.
As with other devices, sleep tracking is kind of hit or miss; if I track my sleep with 5 devices, I get 5 different answers in the morning. The Zepp E doesn't seem much better or worse than other wrist-based wearables in this category, but the Band 5's inaccurate HR readings made its sleep numbers pretty far off. One annoying feature of the Zepp platform is that the app doesn't show a scale next to the HR graph, which seems like a really odd omission. Hopefully, that will be fixed. As befits health-tracking devices, the Zepp app has lots of screens where you can enter your other health data (like BMI, hydration, etc.) I'm not zealous enough to use any of that, but it's there if you want it. Like the other wearables from Chinese companies that I've tested, there doesn't seem to be a way to get detailed analytics on the web or download your data. However, Zepp does connect with Google Fit.Picking a Device to Get Started With Digital Health
If you want a simple and unobtrusive device that keeps an eye on your overall wellness, the Oura Ring 2 ($299 direct(Opens in a new window)) is still a great choice. In addition to baseline health stats, it gives you a loose idea of whether you're active enough, how well-rested you are, and offers a variety of different breathing and meditation exercises. Your data is available through a very nice web interface and for download.
If instead, you're looking for something with more exercise features that also has a full suite of health metrics, both Garmin and Fitbit offer a range of devices that tie into a powerful ecosystem. My overall favorite is my Versa 2, or the very similar Versa 3. While the Sense adds some additional features, you have to stop and use them explicitly, which makes me question whether they are worth the extra $100. And it probably goes without saying that if you want the most powerful and flexible smartwatch, the Apple Watch 6 is the popular favorite.
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