The NHTSA has asked for phone manufacturers to embed technology into their products in order to prevent drivers from using their phones whilst driving. Whilst I agree whole heartedly with the concept I can see no. way of implementing this in a way that doesn't cause all sorts of problems.
Technology isn't always the answer - and in this case it is definitely not a good answer. Any technical solution can either be easily defeated or around. At best technology can be used to provide supporting evidence to allow prosecution.
The cure here is probably punitive legislation and extra enforcement.
Making the punishment so severe as to be a true deterrent is a particularly appropriate option here. A significant driving ban and confiscation of phone and / or car should be enough to persuade drivers to pull over before handling that phone.
With Bluetooth technology all but ubiquitous in new cars and Apple and Android car options becoming more popular there is no reason why anybody need put themselves or others at risk to send a message or take a call.