A washable heart rate strap comfortably conforms to your body. ANT+ 2.4 GHz and Bluetooth� Smart wireless digital heart rate sensor. ANT+ and Bluetooth� Smart allow simultaneous use of Trip 300 and smartphone. For use with all ANT+ and Bluetooth� Smart wireless technology-enabled devices. Includes a washable soft strap, heart rate sensor and CR2032 battery. Visit thisisant.com for a complete list of compatible devices. Visit bluetooth.com for a complete list of compatible devices. Not for underwater use.