The device is put under your sole of the specially made Nike shoe and every step you take is recorded onto your ipod nano wirelessly. Then you can upload all your stats of your run, and check out your goals and more!!
The only thing that isn't nice about this, is that you have to buy the device & the special Nike shoe!!! So you will probably spend around $100..
Thanks to the help of digg.com I found out a hack for the Nike + iPod nano so you can use this new device on any shoe!!!!
Basically this guy sewed a velcro strip on the tongue of his shoe and glued the other vellcro strip to back of the ipod/nike device. Then he attached the device and secured it with his shoe lace (see picture below) And it worked!!! So he can record all his runs and still use the normal running shoes that he loves!!