It wouldn't be that great of a challenge to have an aftermarket accelerometer and ROM mounted to the chassis, and connected via bluetooth to a phone. If the accelerometer detects a crash (so many m/s^2 for so many ms) it instructs the phone to place a preprogrammed call.

If the phone is clipped into a mount, it probably won't survive the crash, slamming around the cabin. But, if it's in a pocket or purse, it probably will.