Look out! I'm on the phone!

You know when someone's acting like an idiot at an intersection? They miss their turn at a four way stop or they're making some crazy-ass right turn from the way far left lane, slowly, though, and with maximum exposure and danger to both their life and yours and everyone else's? And you're like, "This motherfucker's on the phone," and it turns out that they are so you honk and yell at 'em, "Hang up the damn phone!" as if the person on the other end is going to hear you and the offender will somehow be shamed into paying attention to what they're doing? And then the person you're on the phone with is like, "Hold on, some jerkoff is yelling at me"? Or maybe the idiot in the intersection is on the hands-free. You think, "This phone-talking moron is going to kill everyone" and then he pulls alongside you and there's no phone at his head. "This regular, every-day moron is going to kill everyone." And then he starts blabbing away to an empty car and it's obviously not singing because no one listens to anything besides KEXP and you're listening to KEXP and it's an instrumental track currently. "Hands-free moron." What we need are gigantic signs on top of everyone's car, like the ones that are on top of cabs or student drivers, that light up when you make a call: "LOOK OUT--I'M ON THE PHONE." A law is a good start, though. It's not going to stop people from talking hands-free or from reading and responding to text messages or from spinning the little wheelie on their iPod or from keying a street address into their little Garmin doodad or replace common sense in any way shape or form, but it's a good start.