As I am always on the lookout for interesting apps, I have just recently stumbled across two apps which can help towards better driving.
The first you may have heard of is Text n Drive Safely. This app will read aloud incoming texts and emails (data plan needed) and let you respond and send by voice commands. A couple of times I tried it, it had problems "listening" to me, and occasionally got a word or two wrong. This may be due to our kiwi accent. You can get it from the market by going here and if you tweet as well as promote it on Facebook, you can get the Pro version for free.
The other app which I have yet to try is iOnRoad Augmented Driving. This uses your devices camera and GPS, to monitor the traffic ahead of you and warn you if you are following too close and potential crashes in the making. iOnRoad warns you with visual and audio alerts. I will be trialling this today, but won't be following close, just so I can see how accurate it is. :) You can download it here.