Azume One: a Tiny Fitness Tracker for Classic Watches

Startup Azume has announced One, a fitness tracker designed for people who prefer to keep wearing a classic wristwatch. Instead of a strap or a screen, the device is a small module that attaches to the case back of an existing watch and records health and activity data.

The tracker is a disc 30 mm in diameter, 2.8 mm thick and weighing 5 g. It is held in place by micro-suction cups, so it can be moved quickly from one watch to another. All data is viewed in Azume's own app.

What it measures

According to the developers, One tracks heart rate, heart rate variability, blood oxygen saturation, stress levels, recovery after workouts, and sleep duration and phases. On the activity side it counts steps, distance and calories burned, and it recognizes around 30 types of workouts, including running, cycling, strength training and yoga.

One charge lasts 48 hours, and a full charge takes about 30 minutes. The device is protected against water and dust. It cannot mirror notifications from a connected smartphone, which sets it apart from most smartwatches. Data can be synced with Apple Health and Health Connect.

Price and availability

Azume is currently raising funds on Kickstarter, where the package costs €110. After the launch the price is set to rise to €150. The first deliveries are planned for December 2026.

For wearers of mechanical or analog watches, One offers a way to get health metrics without switching to a smartwatch. The trade-off is clear: no notifications and no display of its own, but a very thin, light add-on that moves between watches.