A blogger at the Baltimore Sun found an Apple patent filed last month that describes a multitouch interface for manipulating "three-dimensional virtual objects." The patent seems pretty vague in terms of implementation, but essentially Apple is citing a way to control 3D objects, whether they be icons, game objects, or characters, with a two-dimensional multitouch screen. Sounds like what you're already doing with a game like Zen Bound.
Given that "the tablet" is the hot thing to speculate about lately, there are rumors bubbling up that this type of navigation and manipulation could be found in Apple's new device. But that doesn't seem very likely -- most of what we've heard about the tablet is that it'll offer a higher resolution version of the iPhone's interface, and Apple has no reason yet to step away from that. It's possible that this patent could be covering a new app set to release on the tablet, but of course as with everything here, we'll have to wait and see what Jobs shows us on stage later this month.