i3D is a new app that can create a glasses-free 3D display on iDevices, using a technology known as Head-Coupled Perspective (HCP). Developed by the folks from the Engineering Human-Computer Interaction (EHCI) Research Group, HCP uses a front facing camera to track the movements of a user's head, allowing the app to adjust the display accordingly. The result is a monocular 3D screen that creates the illusion of looking into a box. If the concept sounds a little familiar, it could be because Google unveiled a similar headtracking feature for Ice Cream Sandwich during the opening keynote at this month's I/O event. And by "similar" we mean "pretty much the exact same thing." i3D is now available for free in the iTunes Store and runs on the iPad 2, iPhone 4 and fourth generation iPod Touch. You can compare both iOS and Ice Cream Sandwich 3D generators after the break (Google's demo kicks off around the 16:50 mark).