[Android] I need a workout app that can alternate between pushups and situps or abs

Let me clarify, what I need is this:

1) Config the app for a routine of pushups and situps.
2) The app tells me that the pushups will be 5 series of 10 pushups and the situps, 5 series of 15 situps.
3) Start the pushups, and when the pushups are finished, then start the situps immediately.

This is be a big time saver for me, there should be some app like that in the market... right?

I'm currently using "Just 6 Weeks" app, and I need something better =)