Every time something like this pops up, I'm reminded of a line from a silly book I read as a kid:
"When technology advances, the technology to outsmart it advances too."
The people making these regulations don't understand car people. That cute little mandatory device will be defeated, and a workaround will be sold, within the first year. The same thing happened with diesel trucks - EPA mandated emissions controls were built in the sloppiest possible fashion by engine manufacturers, and when these expensive trucks started needing thousands of dollars of work with fewer than 100,000 miles, people started disabling the emissions controls.
The same thing will happen with this regulation. It will be implemented in the cheapest, most failure prone way possible to save Ford or whoever $5 per unit. Drivers will start having problems with their whiz-bang fancy electronic DUI detector bricking their car, and boom, now there's a market for disabling or removing the devices.
Also, just to attract more downvotes - there doesn't seem to be any similar regulation being pushed for motorcycles. Consider a Goldwing instead of an Accord?
I dunno, I'm not saying it won't happen, but I do think it'll be pursued by the law quickly. This would at the very least open up developers/sellers of this hypothetical device to civil lawsuits due to enabling drunk drivers who then hurt or kill victims.