The Tacx Heart Rate Belt uses sensors to transmit your heart rate wirelessly via ANT+ & Bluetooth technology. The Tacx Heart rate belt can be used with Tacx Smart trainers but also when cycling outside or doing any sport. The Tacx Heart Rate Beltcan be combined many other devices, such as a sports watch, sports applications on a smartphone & a tablet, a Garmin device & a Tacx trainer, making performance tracking convenient & straightforward. Its also water-resistant!