The NTSB recommended alcohol impairment detection systems be included in new vehicles a few months ago. Presumably, those systems would prohibit engine startup or something along those lines if they detect alcohol. I remember the news of this recommendation making some waves due to potential privacy concerns and manufacturer lockout from a device that the person owned, but the general concept is interesting at least and would save lives if there was an ethical (in the sense of ownership), non-intrusive way to implement such systems.