Just be aware that defamation laws still apply even if it's not illegal. Poorly thought out displays of video can still have severe consequences.
I would love to have an onboard camera too however, and with motion detecting for when the car is parked. Some years back my new car (2nd hand but first day I had owned it) got keyed in the car park as I was doing the change of ownership thing. I came outside and nearly died. Even though the car was insured earlier that day I just couldn't bring myself to go back to the insurance and say it had been keyed that afternoon. Video proof would have given me the confidence to go back and see the insurance company.
