Developer of some popular games on the iPhone App Store including Sway, Labyrinth and Touchgrind, Illusion Labs today presented a technical demonstration of a game being controlled only by the trackpad of a MacBook Pro. Since their surface supports gestures of up to four fingers (in most recent), of course they can be used as a control for games in the same way as possible on iPhones and iPod touch.
You can check it out by watching the following video:
(youtube) http://www.youtube/watch?v=FsfROlawZoQ (/ youtube)
Illusion Labs has no plans to launch a product as presented above, but the idea of it could also be explored with a little more attention by Apple. MacBooks with multi-touch trackpads have been around for a long time, but little information regarding the operation and handling of their use is available to developers.