I still don't see what the big deal is about texting and driving....
Click the microphone button (I made mine an 8x8 icon to fill 3/4 of my primary home screen) say "text to victoria" small pause "if you make my phone bark one more time I'm going to feed you to your three dogs when I get home." This has been built into android forever. For iSheep, yes Siri allows you to do this (now) if your using an iOS 6 device.
All joking aside though, to think that your phone would bark at you nonstop until you disabled it would be as much or more of a distraction than sending the text itself as users are digging through their phones menu's to try to stop the barking, all while driving. If they aren't intelligent enough to pull over to use the phone for texting, why would they start doing it for for a barking phone?
I still say a Faraday cage built into the automobile is the only way to go.