I have this app on my iTouch called Body Fate. You select what level of fitness you are, what equipment you have and how long you want to work out. It is a mix of cardio moves and strength training. You also get 3 optional rest periods. It generates a work out for you. It's fun and I've never had a repeat work out.
I am not sure if you can use it through iTunes. I don't have a Mac, but I thought I'd tell you about, since you know your Mac's capabilty better than I do.
HTH
Jen