im pretty sure PDC would go solid beep sooner then 1" so it would be useless. Someone can correct me if I'm wrong.
I would highly suggest some wheel chocks instead, the distance from the front of your wheel to front bumper do not normally change =)
something like this
http://www.griotsgarage.com/product/...arking+stop.do
I'm not advertising for this site, It was just the 1st hit I found on google. shop around if you decide to go this route =)