The Blackvue looks interesting though, simply for the motion sensor while parked (I've had a few friends get their cars dented in while unattended carparks recently), but it's a hell of a lot more expensive at £360 (I got mine on a special so only paid £230 at the time) and obviously it would only work if your car was struck directly in front or behind (as it seems it is a two-camera system).
there are several models of Blackvue, the 500 has wireless for around £260 so you can load events onto your smartphone, the 550 adds the second camera channel. I'm still undecided, I found this chinese one, £90 includes GPS in the mount, Mini 0801 Car DVR
Some great compilations of accidents captured on car cams on youtube, just search for "russian car camera". Actually, great is the wrong description - just shows how fast things can unfold and it'll make you feel (a bit) better about the driving standards here in the UK. And the standards of our roads as well.