We build a webcam fitness platform, so you might expect this article to conclude that webcams beat fitness trackers. It won’t, because they don’t — they measure different things, motivate through different mechanisms, and the honest comparison is about which failure you’d rather live with. Here is how we actually think about it, including the parts where a $30 wristband beats us.
They measure opposite halves of exercise
A wrist tracker measures physiology: heart rate primarily, and movement only as a wrist-mounted accelerometer can guess it. A camera measures kinematics: what your whole body is doing in space — but nothing about what it costs you internally. This one distinction generates almost every practical difference:
| Wrist tracker | Webcam pose tracking | |
|---|---|---|
| Sees | heart rate, wrist motion, steps | whole-body movement: jumps, squats, ducks, leans, cadence |
| Blind to | form, range of motion, lower/upper body split | heart rate, internal effort, anything off-camera |
| Calorie basis | heart rate + accelerometer models | movement classified into MET intensities (methodology) |
| Works during | anything, anywhere, all day | dedicated sessions in front of a screen |
| Cost | a device you buy and charge | the laptop you already own |
| Makes exercise fun | streaks and rings | the activity itself is a game |
Where the tracker wins
All-day coverage is the big one: a tracker counts the walk to the shop, the stairs, the restless afternoon — a camera only knows about sessions you deliberately start. Heart rate is the other: it reflects true internal effort, including the ways fitness changes it. As you get fitter, the same jog costs your heart less, and a heart-rate-based estimate tracks that adaptation; a movement-based estimate like ours credits identical movement identically, fit or not. If your goal is a total daily energy picture or heart-zone training, the wristband is simply the right instrument.
Where the camera wins
Whole-body truth. A wrist tracker fundamentally guesses what your body is doing from one arm — bodyweight squats barely move a wrist, and plenty of honest movement reads as nothing. A pose model watches the actual movement: in a CamPlay session, a squat is detected as your hips genuinely dropping, a jump as your head and hips leaving the ground together, jogging as the full rhythm of arm pump and head bob (the detection details are documented here). Movement variety gets seen and credited — which also means it can be a game control, and that is the deeper difference.
A tracker measures exercise you must independently motivate yourself to do. The camera flips the causality: the exercise happens because you are playing. Ducking a swooping raptor in Dino Dodge or holding a speed tuck through a banked curve in Ski Slalom is a squat you did because the game demanded it, not because a ring told you to close it. For people whose barrier is boredom rather than knowledge — most people — the motivation mechanism is the product. Gamified movement only has to beat the workout you skipped.
Accuracy, honestly
Neither device measures calories; both estimate. Wrist trackers run proprietary models over heart rate and accelerometry — independent studies have repeatedly found their calorie estimates can miss by large margins on individuals, and you cannot inspect why. CamPlay runs a deliberately simple, fully documented model: movement intensity mapped to standard MET values, integrated over time, scaled by your weight — conservative by design, zero credit when the camera can’t see you, and every constant published on the methodology page. We’d summarize it this way: the tracker’s estimate uses richer physiological signal; ours is more transparent and harder to fool. For the purpose that actually matters day to day — comparing your own sessions to your own sessions — consistency beats absolute precision, and both approaches deliver consistency.
Privacy is not a tie
A fitness tracker is a sensor you wear that continuously syncs your physiological data to a company’s cloud, governed by policies you accept and cannot verify. CamPlay’s camera pipeline runs entirely on your device — the video is processed in your browser and never uploaded, which is an architectural property you can verify with devtools, not a policy you take on faith. What leaves your machine is a score and a calorie estimate. If minimizing cloud-resident health data matters to you, the camera approach — counterintuitively — is the conservative choice.
The realistic answer: they stack
The combination is genuinely better than either alone. Wear the tracker for the all-day picture and heart-rate ground truth; use motion-controlled games as the thing that gets you moving hard on the days nothing else would. A pleasant side effect: a CamPlay session is real jogging, jumping and squatting, so your tracker credits it too — same workout, two estimates, and comparing them across a month is a better education in fitness-number skepticism than any article, including this one. If you want to run that experiment, any game here is free; we’d suggest starting with Rune Run and your own two feet.