Ok, there's a technical definition for "hologram" which the Heliodisplay doesn't meet. But, it does achieve the star wars effect nonetheless, and that's what's cool about it.
OK, how does this work? What are the basic physics behind the technology? You can't project on "air" as far as I know because it is transparent so the light won't reflect. Anyone know how this sucker works?
Nevermind. http://en.wikipedia.org/wiki/Heliodisplay explains it. The projection surface is actually a very fine ist being sprayed. That makes perfect sense, the original website doesn't mention anything about water.