I've been asked several times this week whether Apple could or should use the new M7 motion coprocessor chip in the iPhone 5s to lockout features like texting if it detects you're driving. It's an interesting idea but not a particularly workable one, at least not yet.
First, texting is only one kind of distraction. You can be distracted by tweeting, searching for music, using turn-by-turn navigation, or any number of things. You can also be distracted by the newspaper or map you've laid out across the steering wheel, the sandwich you're eating, or the makeup you're putting on.
Second, even if we take the view that M7 could mitigate the problem by locking out purely digital distractions, how would it know you're actually driving the car rather than sitting in the passenger or back seat, or sitting on a train or a bus? And if it can be disabled under those circumstances, the same type of people foolish enough to drive while distracted would likely be foolish enough to disable it under the worst of circumstances too.
Distracted driving of all kinds is a lethal problem. M7-based lockout, by itself and as presently implemented, however, doesn't seem like a realistic solution. We'll have to see if things like iOS in the Car offer any better alternatives.