breathalyzers have always been the thing here, with ours you blow down a plastic tube but i think NSW use one where you just say your name into it and it detects the alcohol in your breath. it says little about the person theyre testing tho, and the simple fact is that a lightweight might end up falling asleep from half a shot of whiskey while a hard drinker could have half a slab and it doesnt hit the sides. kind of hard to work out where the line is, because this is one of these things that *does* kill people *other* than the drunk person, and in the case of alcoholic parents they quite often kill their own kids by accidents, leaving them in cars, shit like that.