Fitbit has launched their first big watch update since March 2018 – the Fitbit Sense. With the new watch comes a range of new sensors: an ECG which is in the same vein as the new Apple Watch and the Samsung Galaxy Watch 3; a stress sensor in the form of electrodermal activity (EDA) galvanic skin response sensor; and a temperature checker that’s something like the Oura ring.

Scott Stein at cnet was sent a Fitbit Sense to test out but the beta version wasn’t able to match with the company’s app. However, the $329 (£300, AU$500) watch does at least look and feel like a better build than the Fitbit Versa. The watch is more curved and is about as thick as the Versa 2 that came in at $199, but the finish has more metal and more glass to it.   


Fitbit Sense


Image credit: ixbt.com

Rather than the old side button that would get a workout going or connect to Amazon’s Alexa – now with added Google Assistant – you get an indented area that will give a little vibration when you press, just like the Fitbit Charge 3 and 4. Whether the sense will perform better when dripping in sweat remains to be seen. Included in a speaker that works for voice assistant and to make calls. To get the straps off is loads easier than on the Versa, giving you more excuses to change up for some custom straps. The charger has been redesigned, it snaps on with magnets and is reminiscent of the Apple Watch system. It supposedly gets a full tank off a 15-minute charge. It’s a big improvement on the alligator clip style charger that you get with the Versa. 

Some other changes have been made that were long overdue. You now get GPS, a revamp of the heart rate sensor which should be more accurate during a run or sleeping, and hopefully, better quality data collected for use in health research – the optical heart rate monitor checks your blood oxygen, heart rate, and respiration and Samsung are working on a blood pressure sensor at the moment. Included in Fitbit’s latest software package is a SpO2 blood oxygen reading capability, which produces a “stress readiness” score to be combined with respiratory rates. This change also comes with the next new model down – the Fitbit Versa 3 which is $230 and also came out on Tuesday. 

The rather ambitious addition of three new sensors to the Sense is a nod from Fitbit that it’s working towards gathering new data for analysis that will feed into a larger picture of machine learning in health. It seems the Sense is Fitbit’s go at the super-wearable health and wellness gadget. Stein sees it as a welcoming idea to get to grips with our daily health that goes beyond step counts and calories burned.

The concept of the super-wearable has been kicking around for a few years, will the Fitbit Sense squeeze into the space? Without a full review, it’s a solid maybe. The business model of Fitbit seems to be moving towards its premium subscription service that came out in 2019, aiming to take advantage of all the data being collected – we’ll go through more as we get through this. 

Fitbit Sense: Design details

When a wearable adds a new sensor, it doesn’t always go smoothly. Is Fitbit breaking new ground with its innovation? Possibly… Think back to other wearables that offered us new sensors – the Jawbone Up 3 and its bio-impedance; Microsoft’s Band 2 with its UV sensing; and the Samsung SinBand that was packed with sensors – few lived up to expectations. Can the Fitbit’s EDA really make as much of an impact as the company claim? We’ll have to wait and see. Doing temperature checks is pretty novel, but the ECG is now becoming a standard of fitness tracking watches.

Fitbit Sense vs Fitbit Versa. Image credit: techadvisor.co.uk

We’re yet to know how these will all work together. The people who should know are Shelten Yuen from Fitbit, the head of research to be precise, plus Conor Heneghan who’s the lead research scientist at Fitbit, and Stein spoke with them to learn more about the new sensor technology. 

Temperature: It’s not a thermometer but it’s useful

Being able to take a temperature with a wearable device has got a lot of attention during the coronavirus pandemic. Being able to detect fever, one of the most common symptoms, through a watch or ring, along with pulse oxygen levels, has become a major ambition. 

“The origin of this was pre-pandemic,” said Yeun over Zoom. “A while ago, we had this hypothesis that with a wearable device, the temperature sensor could be used to detect a fever and even predict a fever was going to occur.”

For a temperature wearable, the $300 Oura ring has taken a big chunk of the market – there isn’t all that much competition. The Fitbit Sense is a similar operation; the temperature of the skin is taken during sleep and the results come in the morning to show the long-term change.

You can’t do an on-the-spot scan of your temperature and there’s no way to confirm if you’re at 98.6 or 100.3. What you do get is a relative change in temperature day-to-day. The readings you can get of your temperature from the skin on your wrist isn’t like on your forehead. Stein wore an Oura ring for a little while and got a graph showing gentle changes over time, but without any sickness during the time, it was hard for him to gauge any level of accuracy. Knowing your relative temperature change is useful to feed into everything else the Sense collects to get your daily stress score. 

What you probably didn’t expect was Fitbit telling you that there’s always been a temperature sensor inside the Versa, but it was reserved for internal battery management. Having that inside previous models has enabled Fitbit to understand what the sensor was capable of. “We have some data from that to direct where this could go in the future,” Heneghan says.

Image credit: newsonnews.com

The battery sensors in older models weren’t so focussed on the skin, so aren’t as accurate. However, there’s a possibility for them to be repurposed to make Fitbit Versas a temperature-checking wearable. This would increase the amount of data that Fitbit can analyze tremendously. 

A new app for checking your stress

The new electrodermal activity (EDA) sensor on the Sense works through the metal rim of the device to conduct and receive readings when you hold your palm down against it. To take advantage of the sensor, there’s a whole new EDA app that will take regular readings and get to understand your overall stress levels. The Relax app that uses your heart rate to calculate your heart rate variability (HRV) and encourages mindfulness. There’ll be new mindfulness and meditation options added to the premium subscription that will also take advantage of the EDA sensor.

“Your body’s sympathetic nervous system is sending little signals to your sweat glands all the time,” Heneghan says of the EDA sensor. “That creates a tiny bit of extra moisture to your skin, and that changes the conductivity of your skin.”.

The app has a two-minute stress scan feature that needs you to keep your hand over the watch during the scan, just like if you were doing a meditation that uses the EDA feature.

“You put your hand over the device, and basically it is a very, very small microcurrent that’s going through the palm of your hand. And we can pick up the individual spikes of nerve sympathetic nervous system activity,” adds Heneghan. “In the EDA scan app, we’re going to count up the number of spikes we see every 30 seconds and report that back to you.”

No arrhythmia scan with the ECG 

In the Fitbit Sense you get a one-lead electrocardiogram (ECG) sensor that you use by pinching the metal bezel around the edge of the watch with your fingertips. This completes a circuit so the watch can scan for potential atrial fibrillation in much the same way as the Apple Watch does, as well as recent Samsung watches and devices like the Withings Move. Like other watches, the ECG can’t tell you when you’re having a heart attack, you’d need much more advanced ECG readings for that. The Sense still hasn’t gotten FDA clearance but it should be through by the end of the year. 

There’s also no constant scanning from the Fitbit Sense, so it can’t detect issues such as arrhythmia quite yet. The Apple Watch has the feature and Fitbit says that they’re working on a fix to add it on.  

Improving heart rate readings to unlock more potential

High expectations have rarely been met when it comes to wearable sensors; we can’t tell how useful the results will be. The sleep apnea detection from Fitbit was promised long ago but still hasn’t materialized after years of waiting. “We are kind of engaging with the regulatory process, and the real challenge is just getting enough volume of data to prove out what we already have,” says Heneghan when quizzed about the detector failing to materialize. 

Other research initiatives that are ongoing at Fitbit include sensors that could forecast wellness through temperature readings and SpO2, or pulse ox, readings. There aren’t yet specific plans, though, nor any studies underway. “In the future, we hope to develop a regulated SpO2 feature that could help with illness detection and maybe an indicator of potential chronic respiratory conditions, like COPD (chronic obstructive pulmonary disease), or acute illness like COVID-19,” the CEO of Fitbit explained to Stein via email. 

There’s research into detecting symptoms of COVID-19  that’s focusing on variability of heart rate, resting heart rate, and metrics around breathing rates. CTO at Fitbit, Eric Friedman says they “can detect 50% of COVID-19 cases a day before onset of symptoms with 70% specificity.” Sleep data will be added by Fitbit, along with SpO2 and temperature details to future studies. 

Improving heart rate readings seem to be feeding into getting more accurate data for running and sleeping so the data doesn’t have so many gaps. There are other possibilities with these improvements, too. In collaboration with Valencell, Samsung is trying to figure out how to take blood pressure with a PPG sensor. It’s not on the radar at Fitbit as yet, but Park says, “When it comes to heart conditions, we continue to explore additional metrics like pulse arrival time – a metric that might signal that your blood vessels are getting stiffer, which could be an indication of heart disease or high blood pressure.” 

There are other bits of information we can get from heart rate data. Yuen notes, “We’re hoping to explore this data set and then maybe unlock its potential in the future. I don’t want to over-promise. But are we interested in things like this? Absolutely.”

Fitbit really wants you to pay for Premium

If you want to access most of the measurements and information we’ve gone through, you’re going to have to pay for the premium subscription which is $10/month. It was launched last year and currently has more than half a million people signed up. You can still get some data for free, like a SpO2 measurement, and there are limited reports on the free version of the app. To store more historical data and get more analysis you need to pay for premium. 

As well as the extra expense, you get tied into the Fitbit system. The data from the wearable doesn’t feed into Google Fit or Apple Health like some other watches. You’re very much stuck with the Fitbit brand and that’s a little limiting, particularly when there’s going to be more health data coming from more sources.

When you but the Sense, Fitbit gives you a six-month trial of the Premium services, and a year’s trial if you go for the cheaper Inspire 2. At some point, you’re going to have to start paying. There’s nothing comparable with Google or Apple in terms of the health and fitness apps, but there are lots of apps in the coaching and fitness sphere that have monthly fees.

It feels a little unnecessary to go for Premium, although a lot of what you get with the Sense might also need it if you want to get the most out of your new device. 

How does this play with Google? 

Google has been in the process of acquiring Fitbit since November 2019 and the subscribers that Fitbit has, along with the reams of data in its archives, could help Google take wearables to a whole new level. There’s nothing new about the Fitbit Sense that ties it into the Google ecosystem, bar the addition of Google Assistant support along with Alexa. Park wouldn’t be drawn to talk about Google. “As you know, the merger is subject to customary closing conditions, including regulatory approvals. Until the transaction closes, we continue to operate independently and are focused on continuing to create exciting, innovative devices and services for our users.”

The Sense from Fitbit could well be the last device under the Fitbit brand. It could also be the blueprint for what we can expect in the future. The new sensors are where Fitbit sees value. There’s no way of knowing how close to the present Fitbit’s future will be as Google steps in to take the helm.