tail light with lasers!
 

http://www.keygos.com/product_info.php?products_id=1178

Good idea or crazy?

Useless. Will not be visible from a vehicle. The maximum legal power output from an unlicensed laser is 5mw. That's 0.005 watts. In a point beam right into someone's eye that's pretty bright (hence the restriction) but spread it out over 5 feet and point it at dark grey asphalt and you'll barely see it standing next to it at night. Under any level of ambient lighting or from a moving vehicle, I doubt you could see it even if you knew it was there and you were looking for it.

This idea was floated about 2 years ago, there are plenty of threads about it. If anyone ever made a commercial product out of it before, it was not successful.

+1. Good idea, doesn't really deliver on the promise. I know handful of people that have these and the tail light is visible but the lines on the ground are not very visible from a motor vehicle.