I bookmarked this video a while ago because it caught my eye but needed further consideration. The Helio Display "mid-air projector" (video below) from io2Technologies projects images from a variety of possible sources onto a condensed plane of air created by a blower. One can interact with the image (click, rotate) as you would any computer with a pointing device. (I was curious how this works, but the product literature and FAQ don't say much.)
Once I moved past the "gee whiz" factor and seductive analogy to the Princess Leia projection scene in Star Wars, I'm less impressed. In terms of real-world utility, the system offers no real advantage over screens. The fact that the display must be projected means it's a two (three if you count the video source) part system that actually requires quite a bit of space. Rather, I most expect to find this display as foot-traffic bait at trade shows and Sharper Image. (This has trade show written all over it.)
Or maybe it's the utter awfulness of the local-news "technology segment" coverage of the invention that really soured me, beginning with "Check this out!" and going downhill from there ("how cool is this?" and "man!"). From me, the Helio Display gets a well-earned, "Huh!"
Oh and Google has additional video.