Heart rate monitors: Chest straps v wrist - Wareable
Amazon.com : COOSPO Bluetooth Heart Rate Monitor Chest Strap H808S, ANT+ BLE HR Monitor Chest, HRM IP67 Waterproof, Use for Running Cycling Gym and Other Sports : Sports & Outdoors
Mo-Fit Heart Rate Monitor Chest Strap for Garmin, Apple, Android, ANT+ – Engine Design Group