If you take training seriously, meet the Suunto Ambit ($550). This outsize GPS watch gauges it all: location, direction, heart rate, calories, distance, pace, temperature, altitude, and air pressure. Post-workout, upload your data to movescount.com, where you can share it with other Ambit users. The Ambit’s one oversight is the lack of a stopwatch, which means it’s not ideal for interval training.