MacRumors has dug up an interesting Apple patent application that would try to mitigate the difficulty associated with tapping while moving (i.e. jogging, back seat of cab, etc.) by dynamically increasing the size of targets in the user interface when it detects jerky motion.
Will we ever see it in an actual iPhone? Who knows. Would it be helpful if, while you're trying to add a potential dates new contact info at the social while getting your krump on, the icons and input areas kept zooming up on you?