I was talking with a member once about ways to combat boredom in the weight room. My advice to him was to listen to podcasts during his workout. Sure, music is a nice mood-booster, but I personally need something more substantial to keep my brain busy while lifting. My favorite podcasts to listen to: This American Life, Radio Lab, Skeptic's Guide to the Universe, and This Week in Tech. All of these and thousands more are free, so if you haven't figured out the whole podcast thing yet, crawl out of that rock you've been living under and get busy.
To call podcasts a "fitness" application of the iPod is a bit of stretch. There are, however, more direct ways to use an iPod to help you workout. PumpOne (formerly called PumpPod) is a company which sells videos of workouts that can be played on any video-enabled iPod. To take it a step further, Apple and Nike partnered together to create the Nike+ running program which, with the addition of a sensor to a specially equipped Nike sneaker, is able to monitor and record your running progress.
Now, in what appears to be the next logical move, Apple appears to be expanding on the Nike + iPod idea to create a "digital fitness companion." From what I can gather, the plan is to make the iPod (with additional hardware to provide feedback) into a mini personal trainer.
Creepy? Just a bit. Cool? Absolutely.