Are there any driving tracking devices that can be used to prove fault in an accident? I was hit by a car that came round a blind bend, on a single track road, too fast to stop. I had stopped before the car hit me and so would have been hit whatever I had done. There were no witnesses and and the driver has no understanding that they were bound to hit anything that was just round the corner.

Can you recommend a device for my car that could have been used to prove I was stopped before impact? Or at least show my speed approaching the corner.
Does one exist?