The 10 Best Basic Polar Heart Rate Monitors – Editor Recommended – PDHRE
Amazon.com : Polar Verity Sense - Optical Heart Rate Monitor Armband for Sport - ANT+ and Dual Bluetooth HRM - Waterproof HR Sensor with only One Button - Compatible with Peloton, Zwift
Apple Watch 4 Review - Sport Focussed (Nike+ 44mm Edition)