Drinking and driving have never been a good combination - even for the ambitious, but this makes an odd kind of sense...
NDrive has launch the first (afaik) dedicated satellite navigation unit to feature an integrated breathalyzer, the 'G400'.
The setup is fairly scientific too with a calibration system employed to analyse the surrounding atmosphere before letting you coat it with your beer breath (though if you're that far gone you'll have probably sprayed it with salvia a number of times by that point and tossed it out the window in frustration).
That aside, once calibrated just breathe gently into a small sensor located on the left edge (note: if telling left from right is proving difficult before you take the test don't even bother).
Sadly, little else is known about the G400 though I suspect it will feature the usual array of POIs, a speed camera database, TMC and European mapping. A low €200 RRP means we'll leave Bluetooth and multimedia playback out to be safe.
No word on when it'll arrive or whether it refuses to work if you fail the test (or if a 'drunk mode' exists which cuts out major roads), but if this is something you think you could use regularly then one tip: take more cabs...