Every golf course has its drunks and, frankly, they are damn annoying. Often stupid. And sometimes dangerous. Those guys are probably too dumb to care whether they are in any kind of shape to drive a golf cart - much less, to drive home after the round.
But social drinkers who play golf might be interested in a gadget called the Golfalyzer. It's a Breathalyzer clone aimed at golfers - blow into it, and it will tell you your blood alcohol level. Want to monitor your level throughout a round to make sure you're not crossing the line? After downing a few more in the clubhouse after the round, want to check your level before getting behind the wheel of a car?
Here's a video, and the guy in it looks like a guy who might need to check his blood alcohol level:
Just remember: Don't drink and drive. The Golfalyzer might tell you you're "legal" to drive home, but any drinking before driving compromises your safety and that of others on the road. Be smart.