Who makes it: Scosche Industries
How much: $100
What it does: This may not be the prettiest product on our list, but the forearm-mounted Rhythm does the trick for measuring pulse, heart rate, distance of your runs and calories burned during workouts. It uses Bluetooth to connect to iOS devices and an accompanying free application takes advantage of Apple's built-in GPS, calendars and other technology to record routes and set workout checkpoints. In a Siri-like voice, it will even let you know how close you are to accomplishing your goal. If you need an added incentive, it can control the music on your mobile device.