Hi, There is company that does this
Free Mobile App Stops Texting While Driving - DriveSafe.ly
They have a blackberry version out now i tried which did email and sms, but think the iPhone one is still being coded but they have one planned.
It has a free version for up to a certain amount of words read out per message, or you can pay a subscription for more features.
You can register to hear when the iPhone version is ready