The lightweight Withings Pulse OX ($100) is a wrist tracker that also clips onto your clothing and measures steps, distance, elevation, calories, and sleep. When you run, the Pulse shows you how long and how far you've gone. It also measures heart rate and blood oxygen level with a single touch of your finger. 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.