I'd like to see it made a secondary offence, enforced like seatbelt laws used to be in Mass.

An officer could not pull you over for not having a seatbelt on, but if he was giving you a ticket for another offense (speeding, etc) and you weren't wearing a seatbelt, it was an additional fine on top of the speeding ticket.

So, if you got into an accident while talking on a cell phone, or were weaving lanes, or committing another moving violation while talking on a cell, the officer could add to the ticket. However, if you were driving in a sane manner but talking on a phone, the officer could not pull you over for that alone.