Some people just love the OnStar vehicular telematics system. In theory it can call emergency services when your vehicle is involved in an accident, can give you GPS-integrated directions to this evening's restaurant, and can even connect you to a service advisor who can help with a startling array of tasks.
Due to the nature of the system, it's always on, which has led to fears of its abuse by privacy advocates. Apparently, they have some cause for concern. Look here for more information from a better-known source.