Heliodisplays 
IO2Technology is working on a heliodisplay. I still don't know the technology behind it, but I am curious to learn more about it.
The Heliodisplay projects full color streaming video into free space (i.e. air). It is plug-and-play compatible with most video sources (TV, DVD, computer, etc.). These non-holographic images can be fully interactive, allowing a hand or finger to select, navigate and manipulate — as if it were a virtual touch screen.
taken from
http://www.io2technology.com/