I don't want to drive drunk

Therefore I would be quite happy to have something built in my car that checks I'm not drunk before I turn on the engine

I'd be even more happy in the very hypothetical case where I'm willing to drive drunk (say a volcano had just erupted) and all it would do is light up a warning light

(that said I know when I've had too much to drink -- like now at 2300 after a succefull 12 hour day, and wouldn't drive, it's when I'm in that 'I don't know if I'm impared state', that's where the breathalyser comes in helpful, so there's no need in my case to do anything with the results other than present them to me)