Quick Take: We selected this particular model from Polar's large catalog of heart-rate monitors and training devices because it popped up most frequently in sports forums. The stainless-steel-framed S720i records your heart rate, your temperature, and your altitude. Of special interest to cyclists, the Polar S720i can collect data on training speed, distance, cadence, and power, though you'll have to buy cadence and power sensors separately. One of our favorite features on this device is the ability to save and recall programmed laps and exercises. You can upload your workout data to your PC via an infrared data link and analyze it later. Unfortunately, the software is fairly bare-bones; you can't get too precise with your data. If your computer doesn't have an IR port, Polar sells an IR interface kit ($34.95 list).