Re: no way of knowing that the person using the phone is the actual driver
A warning, like most GPS navigation systems have, that detects you're moving, warns you not to use the device while driving and has you agree before continuing, may help a few people think twice before they inevitably choose to be an idiot anyway. (I'd like to say it would also reduce the risk of litigation, but someone would likely sue Apple because they [insert incident here] while reading the warning message.)
Still, I can't imagine the pain these parents are going through, and hope I never have to. Just about lost control of my vehicle last night, with my child in the car, avoiding becoming part of a nasty pile-up on i94 that was caused by a combination of icy conditions and, allegedly, a texting driver. Had I lost concentration for split second, I likely wouldn't be typing this.