I thought the air bag module saves "specific data" for a certain number of seconds in a crash. This was originally to collect data of air bag usuage for the manufacturers, but manufacturers kept the functionality there.
Last year there was a bad storm down the highway, about 50 cars piled up, many injuries, and as people were being rescued, more cars piled on. In the end there was an uproar cause the crash investigators used the black boxes in every car with an airbag to lay speeding and dangerous driving charges against anyone who was speeding in the storm, or failed to slow down for the emergency vehicles that were stopped alongside the road.
Their investigation techniquies were challenged in court saying the drivers were not aware they were being monitored. The case failed, half the people got tickets, even when while they layed in the hospital.
If I remember correctly, they were able to detect brake and throttle usage, use of blinkers, etc...