Jaybird Sport Reign
The Jaybird Sport Reign, introduced earlier this year, is built for real fitness geeks. Many devices do little more than plot bar graphs of how many steps you took. That's neat, but not extremely motivating or encouraging. The Reign, however, measures your heart rate variability to predict how ready your body is to handle another heavy workload. It presents this "Go-Zone" score on a scale from 1-100. That's a more meaningful metric that could prevent users from over-exerting themselves. To further help you achieve that goal, Reign makes a daily prediction of how much sleep you really need to be fully functional the next morning.