Wilson Rothman writes: "For a field already glutted with gadgets, the Nike + iPod kit is the most elegant of high-tech runner's aids. An instrument the size of a pebble measures your pace from a pocket inside one of Nike's specially designed shoes. The pebble streams data to a computer that keeps time and calculates caloric burn. Instead of making you buy a whole new computerized accessory, Nike and Apple decided to use a computer you may already own, an iPod nano."