Garmin HRM-Pro ANT+/Bluetooth Heart Rate Chest Strap Only 010-12955-00 - First Class Watches™ HKG
Tutorial - Difference between Heart Rate Chest Strap and Optical Heart Rate Monitor - YouTube
Garmin HRM-Dual - Premium Heart Rate Monitor Chest Strap, Real Time Heart Rate Data via Bluetooth Low Energy, ANT+, Black : Amazon.co.uk: Sports & Outdoors