RunnerGirl77 says:Phaug, a Foot Pod can is, as Nick68 and CarpeViam said, good for measuring your distance when running indoors on a treadmill or track, or measuring cadence. It's measurement is based on your stride length and foot fall. It has to be calibrated, and if your stride is a bit longer or shorter on a given day, the readings may be a tad off. It is not as accurate as running outside with a GPS unit. Why buy it then, when it does basically the same thing as the Nike+ chip? This one talks to your Garmin system, so you can integrate your training activities. Having an estimated measurement, even if it's a bit off, is better than no measurement at all.