We've talked about this before, and Apple's been working on it for a while; as nice as the iPhone and iPad's screens are, there are some functions (like typing on a keyboard or hitting buttons in games) that call for a little more physical feedback. The patent also mentions things like giving users notice when they've reached a limit (as in scrolling or panning across pictures) or providing clicks on a scroll wheel.
Unfortunately, this is all still in the prototype stages. For whatever reason (I can guess a few, from power requirements to manufacturing costs), Apple still hasn't included any of this technology in a production device. But they're obviously very interested in providing haptic feedback, so hopefully, it won't be too long before we see an idea like this come to fruition.