Meet the Smart Buckle: a wearable device that turns any watch into a fitness tracker, allowing you to use your classic watch to count steps and track calories, daily activity, and sleep. It comes with motion and sleep sensors, 1 week battery life, and data storage for up to 2 weeks. You will be able to sync the data to health apps on iOS or Android.
Smart Buckle fits 20mm leather, rubber or cloth watch bands. It is IP57 waterproof rated.[where to find it]