Mandatory Bluetooth car kits

Craig suggested that Bluetooth car kits should be mandatory in new cars. A good idea but I doubt that would make everyone use them. After all, how many people do you still see that don’t wear seat belts, even though they are known to save lives and have been mandatory in new cars for years. Perhaps the idea should be taken a step further by blocking the signal inside the car so that the only way to make or receive calls will be via the installed car kit, whose antenna would be mounted outside the vehicle and therefore not blocked.