Where is the iPhone app that automatically responds to calls and texts with a message that I am driving and will respond as soon as I have arrived at my destination?

AT&T has a drive mode app for android and blackberry. However, I can't find an app for my iPhone 4s that will automatically reply to calls and texts when I am driving. The apps that I see in the app store all relate to parents and teens, and informing parents when teens use the phone or drive out of a prescribed range/area.

Does anyone know how to set the iPhone to auto reply to calls/texts/emails when I am driving, so I am not tempted to respond when I am driving?