For example, the car in front of you is going really slow, you call and say "hi, this is the car behind you, you might not be aware of this, but your going 25 in a 45, if you don't mind could you speed up a bit?"  Or you could just ask them to pull over and let you pass.

Or, you might want to call the car behind you and say "  hey it's me the car in front of you, you may not have seen the cop, but that's why I slowed down, if you could get off my ass that would be great." 

Think about it, have you ever wanted to tell someone you thought their bumper sticker was funny? Or that you liked their license plate?  Well now you could. 

You could ask someone if they knew where the ___ is located, without rolling down the window and yelling, almost causing an accident.

I think my idea is a much better way of dealing with road rage. 

You could commiserate with other drivers when your in a bad traffic jam.

You to car in front of you:  Can you believe this crap?

Car in front of you:  I know, it looks like they're doing construction again, I'll call the guy next to me and make sure he lets us in when were down to one lane.

No need to tell me what a genius I am, I already know.