The Best (and Worst) Fitness Devices I Tested in 2025

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2025 was a fun year to review fitness devices. We saw three companies introduce devices that could have been Whoop killers, and one definitely came closer to the mark than others. One running watch gobsmacked me with its accuracy, one device was so inaccurate it sent me down an investigative rabbit hole to figure out why, and two devices delighted me with how well they solved a real problem no other device even tried to tackle. Read on for the winners of my very subjective award categories.

Most accurate: Garmin Forerunner 570

Garmin’s Forerunner 570 and 970 were new devices this year. I felt ambivalent, on average, about the upgrades they made from previous devices like the 265. But I want to call out the heart rate sensor on the 570 for being so accurate it confused me. 

See, Garmin’s previous watches, like the Forerunner 265, had a perfectly good heart rate sensor. I’d put them in the same tier as most Coros watches, a smidge higher than the Apple Watch, and generally as good as, or better than, most other high-end devices. 

But Garmin put its very best heart rate sensor in the Forerunner 570. This same sensor, the Elevate version 5,  is also in Garmin’s Forerunner 970, Venu 3 and 4, and Fenix 8. I was not prepared for how much better it would be. I test all my devices against an electrical heart rate chest strap, the gold standard for this sort of thing, and a good wrist-based sensor will only show a few small deviations between its heart rate graph and the one I get from the chest strap. But the 570 sometimes showed exactly the same data. The graph below shows what I expect from a good sensor (top) and what I got from the 570 (bottom). Yes, there are two lines in the bottom graph. 

At first I thought I had screwed up, and gotten the chest and wrist data mixed up somehow, maybe uploading the same file twice—that’s how close they were. But with further testing, and also zooming in to see the occasional tiny difference between the two lines, I confirmed that the 570’s sensor really was that accurate. Damn, Garmin. I’m impressed.

Coolest concept (that actually works): Core 2 Thermal Sensor

The summer heat is a problem for every runner in a climate with warm summers. Not only are those hot runs unpleasant, the heat literally slows you down, and puts you at risk of heat illness. If you can manage to adapt your body to the heat, you can withstand it better and make your summer training a lot more bearable and productive. You don’t need a specific gadget to do heat training, but there’s a lot of guesswork in the process, and it’s hard to know whether you’re doing enough heat training (or too much). 

The Core 2 sensor promised to handle this for me, and it worked well. You can read about my experience here. You clip the device to your heart rate chest strap, and it measures your body temperature in two different ways: a temperature sensor detects your skin temperature, and a heat flux sensor paired with a heart rate algorithm delivers an estimate of your core (internal) body temperature. From that data, the device can tell you when you’re hot enough that your workout counts as useful heat training, and it can warn you when you’re getting too hot and need to take a break. 

The biggest downside was that I only got my training data if I wore a heart rate chest strap for every hot weather workout, which I couldn’t always be bothered to do. But once I had gotten through the spring and early summer, and hit 100% heat adaptation, I found I didn’t really need the device. 

I found the device incredibly useful, especially since it could broadcast my temperature data to my Garmin watch during runs. I could also log sauna sessions in the device’s app (without taking the device into the sauna) and see how heat-adapted I was becoming. The data I got from the app seemed accurate, and as a result I had probably my most productive and enjoyable summer of running ever. 

Runner-up: DFC

The Data Fitness Connector is a little box that you connect to the cables on the back of your Peloton Bike (original Bike only, not the Bike+) It felt a little sketchy to order this device from a crowdfunding site with few reviews available, and unfortunately it can only give power data, not speed or distance. But it works! You can read my review here.

I took a chance on the DFC because I had canceled my Peloton subscription, but still wanted to use the Bike and sync my workouts to my fitness watch. The DFC did exactly what it promised: beamed power data over Bluetooth so that my watch or phone could pick up the information and log it in a workout. My Garmin was able to give me an FTP estimate and recommend power-based workouts, and there was no ongoing cost. (The $125 price costs less than three months of the Peloton All-Access subscription.) I can highly recommend the DFC for anyone with an OG Bike who wants to opt out of the Peloton subscription world. 

Best upgrade and best overall: Coros Pace 4

Coros’s running watches tend to lag a little behind Garmin’s, in terms of features, but they more than make up for it on price. I’ve consistently found the Coros Pace line (Pace 3, Pace Pro, and Pace 4) to be reliable, accurate, and conveniently usable. The Pace 3, in particular, has long been one of my favorite budget watches, even though it has a few small downsides. 

But late this year, Coros introduced the Pace 4. Between the new features in that watch, and an extra thing or two that dropped in the December software update, it’s hands down the best fitness watch for the money and is my overall pick for the best fitness watch of 2025. 

You can read my review here to learn more about why I feel this way. In terms of upgraded features, the Pace 4 improved on the Pace 3 by adding an AMOLED screen, better battery life, and a new button and microphone. Those last two items unlock two features that seriously upgraded my runs and training sessions: voice pins, which let me quickly make notes about a location while you’re hiking or trail running, and voice training logs, which mean I’m prompted to record a 60-second voice note right when I finish a workout. 

These notes are transcribed and attached to the workout in the Coros app, giving me information that I would pretty much never get around to adding after the fact. And then the December software update added a major feature that has kept Coros lagging behind Garmin and other watches: the ability to control media that is playing from your phone. The interface for that isn’t as smooth as I would like, but it’s there, and that’s huge.

Runner-up: charging features on the Pixel Watch 4

The next best upgrade of 2025 belongs to the Pixel Watch 4. You can read my review here, where I found the upgrades to be a mixed bag. (Dual band GPS? Great! Brighter screen? Eh, not really.) But the headline improvement here, to me, was the ultra-fast charging. 

I only needed half an hour for nearly a full charge—specifically, I charged the watch from 3% to 97% in 31 minutes. No other smartwatch out there charges this fast. The Pixel Watch 4 also ships with a new magnetic dock-style charger that is far more convenient than the back-of-watch puck that previous versions used.

Best Whoop alternative: Amazfit Helio Strap

This summer, a somewhat unexpected competition popped up: three different device makers (Garmin, Polar, and Amazfit) were rumored to be working on screenless fitness trackers that could compete with Whoop. All three companies released their promised or rumored devices over the following months, and I tested them all. 

Garmin’s device turned out to be a $170 sleep tracker; fine, I guess, but not what so many of us were hoping for. Polar’s $200 device looks and acts more like a Whoop, in terms of hardware, anyway. It’s a welcome addition to the market, since Whoop had this product category all to itself for too long, but I have to admit I couldn’t get too excited about it. 

The winner, surprisingly, turned out to be the Amazfit Helio Strap. At just $99, it does everything the Polar device does, but (in my experience) more reliably, and it costs half as much. It goes without saying that it leaves Garmin’s sleep band in the dust. You can read my review of the Amazfit Helio Strap here. 

None of the devices are even attempting to compete with Whoop’s subscription app on software features, which is to be expected—Whoop is really a software company that gives you a cool gadget to go with the app, while the other companies in this space are hardware companies that figure their app doesn’t matter very much as long as you’re happy with the physical device. I think that’s a fair take on the market: These new products are for people who like the idea of a screenless tracker but don’t want to pay for a Whoop-caliber app. I expect Amazfit will have a lot of happy customers.

Biggest disappointment: Powerbeats Pro 2

The idea of putting a heart rate sensor in your ears is intriguing, and I really wish it had worked out for the Powerbeats Pro 2. But the company that placed their bets on this technology this year—Beats—just didn’t execute it well enough. 

As I discovered through extensive testing (here, and then more in my review here), the heart rate sensor doesn’t make good contact with your skin unless your ears are a particular shape and size. Changing out the silicone ear tips doesn’t change the fit of the heart rate sensor (or at least, not enough to fix the issue), so some people simply end up with unusable or unreliable heart rate data. 

From my limited data, it appears that people with larger ears get reasonably good data, while smaller people may have more issues. I suspect the flaws affect women more than men, but Beats hasn’t shared any data with me that would confirm or deny that hypothesis.

A September software update improved the heart rate algorithm slightly, and included a feature that warns users if their fit is poor enough to affect heart rate readings. That’s a good start, since otherwise you wouldn’t even know if you’re getting inaccurate readings. But if you’re one of the people for whom tweaking the fit doesn’t give you usable data, you’re out $250 for a device that doesn’t actually work for you. On the bright side, they are good gym headphones even with the heart rate feature turned off.