The G1W has a G-Sensor. If it is turned on when you are in an accident the force of impact should auto lock the file from being overwritten. If it is not turned on the mode button will lock the current whole segment of video from being overwritten.
If it is not set and you forget to lock it the camera can run for about 6 hours before it would over write the clip in question if you are using a 32GB card so if you get someone to get the card before then you should be okay.