If you liked Johnny Chung Lee's Wii headtracking tricks you will love iHologram, a stunning iPhone app that makes the screen look like a window to a real, parallel dimension. While it seems like magic, it uses anamorphosis, a very simple painting technique that has been used by old masters since the 15th century, mixed with the technology in the JesusPhone.
Created by David O'Reilly, iHologram combines anamorphosis and the iPhone's gyroscopes to achieve this awesome visual magic trick. Anamorphosis is a way to draw things distorted so, while watched at a certain angle, they pop out of the 2D surface as if they were real.
David's application assumes a constant viewing angle of 35 to 45 degrees, which is the usual angle when anyone watches the iPhone screen. Knowing that angle, the application calculates the orientation of the screen relative to the viewer using the iPhone's motion sensors, so when you turn it around, the 3D world perspective gets skewed accordingly.