The iPod becomes your personal trainer giving feedback on the number of miles you have jogged, you average speed and how far you are from the target destination. You can later sync the workout session with your computer to track your progress.
If you don't have those extra 100 bucks to spare for the Nike sports shoe, the wireless sensor + iPod Nano combination can work with even your existing pair of shoes. No more excuses.
Apple iPod + Nike [Thanks Dave Mozealous]