Found this:
Would it surprise you to find out that the FBI might be able to monitor private conversations in your car? A recent court case revealed that the FBI used the popular OnStar system to do just that.
GM cars equipped with OnStar are supposed to be the leading edge of safety and technology. OnStar has run a recent blitz of commercials citing helpless motorists calling in with every type of emergency, from a heart attack to locking the keys inside the car. In the advertising world, OnStar reacts quickly by sending help or even unlocking the car.
Read the full story at
http://www.tonyrogers.com/news/onstar.htm