The lightweight Withings Pulse ($120) clips onto your clothing and measures steps, distance, elevation, calories, and sleep (it comes with a wrist strap, so you can wear it while you sleep). When you run, the Pulse shows you how long and how far you've gone. The Pulse stands out from the rest, however, with an additional metric: place a finger on the back of the Pulse, and it'll tell you your heart rate. Then, sync data wirelessly to your iOS or Android phone with the free Withings app. The Pulse has a battery life of about two weeks before needing to be recharged.