I think the true potential of Kinect and it's 3D realtime tracking ability will lie in marketplace apps. Thousands of new applications with minority-report-style UIs can be built to do everything from internet browsing to trying on clothes at your favorite stores to video editting. The possibilities are endless.<p>What app would you design?<p>I would create a dressing room application filled with the latest styles from dozens of popular stores, allow the user to try them on in 3D and then quickly make a purchase. I could see this being quite the killer app for shopping...
Note: XNA for creating games exists, but this isn't the powerful app-store / developer API functionality that it would need (<a href="http://creators.xna.com/en-US/" rel="nofollow">http://creators.xna.com/en-US/</a>)