Apple and Nike teamed up to offer a sensor for Nike’s Air Zoom Moire shoes that connects wireless to an iPod nano (presumably not a Shuffle or standard iPod). The NikePlus.com website says that the products will be available on July 13.
The Air Zoom Moire lists for $100. And, the Nike+iPod Sport Kit lists for $29. Nike’s site has an area that appears to let kit owners upload their run data, track their progress, and compare it with up to 50 people in a challenges section. I might start running again just to try this out with my nano :-)