My friend and I were talking about this exact idea the other day. I think it would be great, except if people are pulling over off into the shoulder every 10 feet.

Just last night some woman in a HUGE suburban was at about a 45* angle in the lane next to me I look over expecting to see someone trying to get into the lane that I was in, and she was;
a) smoking while driving(that really pisses me off)
b) talking on her cell phone
c) going through her purse

I wanted to get out of my car and hang up her phone, throw the cig on the ground, and toss her bag in the back. Pisses me off.