How do I have my Galaxy S3 automatically switch into Driving Mode when I am moving in a car? It seems like I read something about how to do this once, but now I can't find it. I thought it was a feature of On{x}, but it doesn't look like the Galaxy S3 Driving Mode is exposed through their API.

What I want is for my phone to automatically switch into Driving Mode when it detects I am moving faster than a certain speed (doesn't need to be immediate), and then when I am moving below that threshold switch back (again, after about a minute).
How about using NFC to tell the phone that it should switch itself to driving mode when inserted into the cradle?
You can get nfc stickers for few euro/pounds on ebay..., put one to the back of the cradle, setup your phone and off you go :-)
That probably isn't what you're looking for but still, it's nice and elegant solution ;-)