Nike+ GPS

Grab your iPod nano and go — no accessories required. Or grab your iPod touch or iPhone 3GS or later, a pair of Nike+ shoes, and the Nike + iPod Sensor. Put the sensor in your Nike+ shoe — there’s a pocket for it under the insole. iPod touch and iPhone 3GS or later have built-in support for Nike + iPod, so no receiver is necessary. [source]