Legislation alone isn't the answer, but making vehicular homicide a strict liability offense would go a long way toward removing prosecutorial discretion from the equation.

I still say it's cultural and the devices themselves aren't at fault. Look at how they build cars nowadays. It takes four steps to get frickin' outside air into my car, poking at indistinguishable buttons and touch screens that, unlike old-fashioned knobs, cannot be identified without looking at them. Mostly I ask my passenger to do it, or if I'm alone, I just settle for heat/AC, which at least is only two steps with those same buttons and screens, and suffer through the dead air. I've ranted before about how it's impossible to take a wide focus between the side-curtain airbags and the aerodynamic windshield, and I have to stick my head out the window if I want to see where I'm going on a left-hand curve.

I mean, if someone thinks they are supposed to be doing something vaguely important behind the wheel, they wouldn't be picking up the phone in the first place.