I've seen the speed alarm thing before, can't remember what brand it is or anything because I wasn't looking to buy one, but it's an adjustible control near the steering wheel so you can set it to whatever speed for whatever road you're on.

I've also seen the anti-drunk tester on cars. There was a test run in like Nevada or something, but it didn't really work out because all you have to do is get some sober person to blow for you while you start the car :dunno:

 

there is devices that can be put in cars that tells parents exactly how fast you're going and where you are and crap. there's some really paranoid parents out there...