There are lots of cars on the road from GM that feature OnStar. The service allows drivers to place hands free calls and dials 911 automatically in the event of an accident. The GPS features of the service can also provide the exact location of the car for EMS and roadside assistance.
A company called Guidepoint has announced a new hands free Bluetooth device that offers some of the same features as OnStar. The device can be coupled with an optional GPS tracker to give positional information for roadside assistance and EMS services.