Don't they say it's not the cell phone, it's the conversation that's distracting? Presumably conversing with your passenger is also distracting? Optimally you want passengers busy texting on their phones and ignoring the driver then.
^ Well, you can talk to your passengers without looking at them. And in certain instances you can use cellphones hands-free without looking at them either. But of course you have to look at a device to use it for texting. That's the problem.
Communicating live in a car is different than over a phone. Fellow passengers, for example, can see the traffic conditions and know when to clam up to allow for ease of driving or know why there's a lull in the conversation. As well as passengers in the car can rely on visual cues from the driver's conversation for easier communication. Talking on the phone you actually lose a good portion of conversing with someone by not being able to see the person. I can't say I've ever seen a study showing it's "the conversation not the phone" since even people with hands-free devices have a harder time driving and talking on the phone at the same time. Talking on the phone is just a completely different means of communication as opposed to talking to someone in person. More is involved in a phone conversation and the other person on the phone doesn't have the benefit of being there to know when to dial back the conversation to allow for driving concentration. The biggest problem, again, I see is having a device that works in such a very narrow area. I mean I don't think electronics, radio-signals or whatever are nearly precise enough to only work in the 2-foot by 2-foot space of the driver's seat and not impact anyone else in the car. Having the "annunciator" idea I suggested above would at least offer something of a solution to discourage texting while driving if not to at least remind the driver to look at the road.
I don't know what kind of dumbass would try to text or use their phone in a non-hands-free manner but if they did, they wouldn't be "shiny side up" very long. I think making the penalty for distracted driving the exact same as one would receive for driving under the influence of alcohol or drugs would help. People clearly don't take it seriously enough. Then again, people still drink and drive, so that may not be so effective after all.