Update (February, 2012): Microsoft Research Applied Sciences Group presented a 3D interactive displays at Microsoft TechForum Feburary 2012, which supported behind the screen overlay interactions with a transparent OLED that has viewer-dependent, depth-corrected gaze.
Update (February, 2013): Video description: "SpaceTop is a concept that fuses 2D and spatial 3D interactions in a single desktop workspace. It extends the traditional desktop interface with interaction technology and visualization techniques that enable seamless transitions between 2D and 3D manipulations. SpaceTop allows users to type, click, draw in 2D, and directly manipulate interface elements that float in the 3D space above the keyboard. It makes it possible to easily switch from one modality to another, or to simultaneously use two modalities with different hands. We introduce hardware and software configurations for co-locating these various interaction modalities in a unified workspace using depth cameras and a transparent display. We describe new interaction and visualization techniques that allow users to interact with 2D elements floating in 3D space and present the results from a preliminary user study that indicates the benefit of such hybrid workspaces."