I am trying to see if there is a way to hack in to the onstar system on a 2005 trailblazer.

The onstar button on the steering wheel shuts off the radio and turns on a microphone somewhere in the car.

It would be cool to link the iphone to this to play sound through the stereo and then hack the microphone on onstar system to pick up calls and use the speakers of the trailblazer as the phone speaker.

still wondering if this is possible. Has anyone ever tried to hack in to the microphone built in to onstar equipped cars to make it work for your cell phone?