CHrissy,
Look up Cardiocoach to get an idea of what these ipod (or mp3) workouts are like. Basically, you get a trainer's voice over music that is choreographed for cardio workouts(elliptical, treadmill, bike,etc).
I just got one for the treadmill based on recs. from this board & I can't believe the difference the music and encouraging trainer's voice have already made in my treadmill workouts!
I would LOVE to hear Cathe's voice & music choices. I think it would be great if the gymstyles for weight training or IMAX3 for interval training were adapted to ipod workouts! That would be Awesome!
HTH