Sports' performance continues to improve thanks to advanced electronics. The latest tool comes from Polar, which is using Bluetooth technology to let coaches monitor heart rates for up to 28 athletes. It can store heartbeat data for up to 48 hours of activity, letting coaches and researchers compare responses under different conditions. The Polar Team2 system gathers data for up to 30 hours from distances up to 100m, even underwater. Team members wear sensors that include CSR's BlueCore4 chips, which send data to a Bluetooth Access Server platform from Bluegiga Technologies.