Even ignoring the privacy problems, and the many technical problems this would run into with false positives and faulty systems, this approach to the problem of drunk driving is misguided.
The US is one of the worst in the world for drunk driving, both in DUI rates, and how much blood alcohol is considered to be a DUI. Other countries are doing things way better than us, and a kill switch isnt their solution. We have shit like parking minimums for bars, and an abyssmal public transit infrastructure. Drunk driving is designed into our infrastructure. Even trying to address DUI convictions after the fact is discouraged here, because taking away someones ability to drive means taking away their functioning in American society.
Everytime ev's come up everyone's a fur trapper in the himalayas that needs to make pilgrimage over 500 miles every other day.