Is anyone familiar with the OnStar service? I am thinking of purchasing a GM vehicle with OnStar but I am not sure how secure the service is.

Is there a way or have there been any incidents where someone tapped into the system? I know the OnStar service provides remote door unlock via a signal. Can that signal be intercepted? I know that most computer-based systems are not totally secure but am just wondering how secure they are. I don't want to have this service if it's going to be an easy way for someone to break and enter. I know it would be less attractive to steal a car with the OnStar service since it is tracked but what about if you have useful stuff in there?

Shoot your ideas my way, the more the better. Thanks