Cateye OHR-31 Optical Heart Rate Sensor:

CatEye:

The OHR-31 is an optical heart rate sensor designed for accurate, real-time monitoring compatible with Bluetooth® and ANT+ devices. It delivers a heart rate range of 40-220 bpm (±5 bpm), making it suitable for a wide range of users and activities.

Features
Easy pairing via smartphone app (Bluetooth®)
Low battery indicator activates below 20% battery level
Red LED blinks every 5 minutes when battery is critically low
Automatically powers off after 15 minutes without heart rate detection
Waterproof construction with IPX7 rating for durability in all conditions

SPECIFICATIONS

Heart rate range: 40-220 bpm (±5 bpm)
Connectivity: Bluetooth®, ANT+
Battery indicator: Low battery warning and LED alerts
Power saving: Auto shut-off after 15 minutes of inactivity
Water resistance: IPX7