iOS (Jailbroken): When you get a new text message or phone call when you're driving, you have to look down at your phone to see what it's about. This means taking your eyes off the road, which is never a good thing (and grounds for charging you if a cop spots yoy). VSNotifications is a tweak that reads your banner notifications out loud automatically.
Siri is handy when you can reach your phone and ask it to read a message, but when you need a hands-free approach VSNotifications should do the trick. It's filled with options to customise how it works, including whether it reads an entire message out loud or not. You can find VSNotifications in the Big Boss Repository on Cydia.