I have a Blackvue DR300G
It is only SD and 4:3 and if fine for recording actions of other drivers but is not high enough resolution to read number plates unless you are right behind someone.
If you can afford it, get something that is 1080p HD.
Race recall
http://www.racerecall.com/cameras-by...49_127_96.html has some that are a bit cheaper than
http://www.autoblackbox.com.au
I need to hard wire mine so i can catch the bugger that keeps backing into my car and bending the number plate and scratching the bumper.