Angelina Just for humor's sake, I am now imagining the breathalizer on a male belt. To have sex with a guy in a belt like that, his partner would need to blow him first.
Either way, a sobriety test for sex seems like it would cut down on things like unwanted pregnancies a lot, but it would probably require widespread chastity belting to be enforcable, and if you are already belting people you are probably also cutting down on "Verkehrsunfälle" in other ways already. But the slogans for promoting those devices in Germany pretty much write themselves, with the double meaning of Verkehr.