The solution to this is simple: one way or another, except for people whose job it is to drive, we should stop having people drive cars, whether that means public transit, more bike lanes, or self-driving cars or something else.

I do think it's possible to approximately locate a driver's phone, though it will likely work relatively imperfectly. But then consider that driving drunk is also a huge hazard, and yet most people don't have breathalyzers required to start their cars (and yes, this technology does already exist)