SMS Audio SMS-EB-SPRT-BLK STREET by 50 Wired In-Ear Sport Headphones, Black BioSport technology is built using an open architecture to optimize compatibility with the world's most popular fitness applications. Users don't need to change how they train to adopt this innovative technology - because that's the way it should be..Applicable for Wired headphones Built-in optical sensor continuously measures accurate heart rate and removes noise signals caused by body motion Delivers precise heart rate tracking and enables peak performance and progress tracking BioSport uses an optical emitter to measure the smallest changes in blood flow through the capillaries. This results in the most accurate detection available for wearable monitors Monitor every heartbeat, every time. There are no bulky battery packs to add weight no charging required. BioSport is always ready to perform - mile after mile after mile