CatEye Heartrate Sensor OHR-31

Optical heart rate sensor compatible with Bluetooth® and ANT+
Heart rate range 40-220 bpm (±5 bpm)
Easy pairing via smartphone app (Bluetooth®)
Low battery indicator (less than 20%)
?Red LED blinks three times every 5 minutes until battery reaches critical level.
Automatically turns off after 15 minutes of no heart rate measurement.
Waterproof construct IPX7