Siri (iPhone 4S and later)
Image via WikiMedia
An iPhone will not automatically detect that you are driving, and it will not, by default, auto-respond or read your messages. But if you notice that a message came in, or missed a call, you can do like Jesse Thomson does and ask your phone assistant, Siri, what is up:
@kevinpurdy I just use Siri through my car’s bluetooth system. “Read Messages” “Tell Julia I’ll be right there.”
— Jesse Thomson (@Braxo) April 16, 2014
Drive Mode, Drive First, Safely Go (Android on AT&T, Sprint, Verizon)
Three of the big four U.S. mobile carriers offer safe driving apps, either pre-installed on their phones (and often impossible to remove), or available as a free download. AT&T has DriveMode, Sprint Drive First, and Verizon offers Safely Go (although non-Verizon Android owners can install Safely Go, too).
Image via Google Play
Consumer Reports reviewed all three of these apps in January 2014, and I agree with their findings. Drive Safe is not bad, though it does take a long while to restore your phone's normal text/call behavior after it thinks you have stopped driving. Drive First takes a good amount of setup to get working the way you want. And Safely Go is a big, cartoon-ish app that does not automatically activate when you are driving. None of the apps are particularly elegant or good-looking, but the first two get the job done.