Who remembers the Nike+ iPod Pedometer? Went in your shoe under the insole and connected to your iPod via a separate 30-pin dongle. : r/RunningShoeGeeks
NEW NIKE+ IPOD Sensor A1193 for Apple iPhone 4S 5S NIKE Shoes Running Sport KIT EUR 4,68 - PicClick IT
Replace Battery in Nike+ Sensor : 5 Steps - Instructables