Alpha is the world’s first strapless, continuous heart rate monitor you can wear on your wrist. It has been tested accurate even while you are running at performance speeds of up to 12mph (20km/h). Before Alpha, the most common way to get an accurate heart rate continuously while exercising was to wear a strap around your chest. With Alpha’s innovative technology, the world of heart rate monitoring will be changed forever. Alpha uses Bluetooth Smart technology to connect with compatible smartphones and sport and fitness devices. USB charging dock with magnetic alignment. Rechargeable lithium battery.