Displaying Images In Thin Air
The Microsoft Applied Sciences Group has been investigating making devices that disconnect the apparent location of a displayed image from the location of the hardware. Such devices can make images appear to "float".
One use is for allowing touch interfaces that don't require physical contact.
Another use is to allow visual affordances for interactions that aren't on a surface upon which to display a normal affordance, such as for devices that sense hover, gestures, or pose.