I happened to stumble on this very interesting application called Nike BOOM. When we think about Nike we think about top athletes and this application helps you to experience being a top athlete yourself!
It works like this: You just pick one or multiple of the many well known athletes and set up a custom playlist. Then you can start working out. Every once in a while the chosen athlete(s) will interrupt the song played and give you a motivating speech. Just like they get from their own personal coaches.
To make this application even better, you can share your work out on facebook. I think this is an important feature, because many people like to brag on facebook. Besides that it also keeps track of your history, so you can check how much progression you have made.
Here is a video that shows the free application
Hope you guys like it