There are tons of distractions within the car - changing the radio, changing the song on your ipod, looking through your purse, eating some food - texting is only adding to the list. THe problem is there is too much for us to do and until all of those things get taken away accidents will continue to happen.
Obviously texting is extremely bad because of the length it takes to read/write a message - but other than cars and phones having a sync to shut down phones within the car - there really isn't an alternative that will be able to stop this problem.
Doubt it would have much impact. People will simply find new ways to distract themselves.