Accuracy and simplicity make Garmin's Forerunner 210 a favorite among the world's best runners. It keeps track of heart rate, time, distance, speed, effort, and your route, thanks to its built-in GPS. It works indoors and out, and is compatible with some indoor fitness equipment. Garmin's Foot Pod accurately tracks distance and speed whether you're on the treadmill or out of satellite range. When you're done with your workout, you can log it on Garmin Connect to keep track of your training.