DriveSafe.ly is still in Alpha and only on jailbreak at the moment. At some point they will release it via the app store, but without backgrounder, I’m not sure how useful it is. The app is simple enough; every 5sec or 1min it checks for new SMS messages. If a new message is found, it converts the sender’s name and message to voice and plays it on the iphone. Natch! The app is still a touch buggy and it does not always work for me, but in the one ‘real’ use case, it proved useful. I normally do not ride with earphones unless it a long ride and if that long ride is mostly freeway.