This tiny foot pod is small enough to attach to your shoelaces or fit in the mid-sole pocket of compatible shoes. It's always ready to use, and a small, replaceable watch battery powers the foot pod for a year of training. Unlike simple pedometers, this foot pod uses advanced MEMS inertial-sensor technology to analyze your movements and is responsive to stride-length changes to achieve 98 percent accuracy for speed and distance. Additionally, this sensor measures running cadence to help you optimize your training. Compatible with Forerunner® 60 / 210 / 305 / 310XT / 405 / 410.