I'm all for for having these mandatory in all cars. Here's my system...If you have a clean record, you'd have to register under the .08 legal limit...that'd maintain the driver's basic freedoms (in other words, if you want to risk driving buzzed, go ahead ya jackass) and effectively eliminate the false positive risk.
If you have a conviction on your record, it's .02. Simple enough IMO.
People will complain about Big Brother, but I'm sure the same thing happened when front-row seatbelts became mandatory, and I don't see our society turning into dystopia because of seatbelts. In fact, this is even more necessary than seatbelts. If you don't fasten your seatbelt, you're gambling with your own life. If you have a few beers and then drive with a .13, your gambling with the life of everybody on the road.
Fact is, we've had automobiles for about a century and the drunk driving problem hasn't even come close to going away. Since we have the technology to save lives, let's save lives.