How Do You Control Music Through the Dock (30-pin)?

I'm looking to build a system to be able to control my media while in my car. I looked at the pinout of the 30-pin connector, but can't see what pins activate things like next song, previous song, and play/pause. Does anyone know how to do this?

I'm going to use a PodBreakout to connect the wires and get everything set up in the car