A couple of guys from the Engineering Human-Computer Interaction (EHCI) research group of Laboratory of Informatics of Grenoble, Jeremie Francone and Laurence Nigay, have done it. They figured out how to bring the 3D experience to these devices without spacial glasses! Check out the full article and videos in iphone Hack.
They have provided the following details on how their system works:
We track the head of the user with the front facing camera in order to create a glasses-free monocular 3D display. Such spatially-aware mobile display enables to improve the possibilities of interaction. It does not use the accelerometers and relies only on the front camera.