Start making sure that insurance companies have no payouts if the driver's phone was on X amount of time before the accident. That way they pay for their own damage, and the damage done to everyone around them. Regardless if they were "at fault" using conventional reasoning.
How about another one: Require all vehicles to install cell phone tethers that have the driver's registered sim card in it. Disable it during the drive. Mandate it's installation, and penalize people that break it, even more so if they were in an accident.
Almost ALL problems have a technical/legislative solution for them. The only real problem is that no one has either the resolve, balls, lawyers, political backing, or money to implement/require those technical/legislative solutions. So all we get are half-asses solutions with selective (and sometimes biased) enforcement by the police/courts.