Peter, Ken and I had a great discussion on crystal ball-based communication. Turns out that a Massachusetts-based company called Actuality Systems has been working on a crystal ball display for sometime now. Check out the photo gallery, it's quite impressive. They even tell you exactly how it works. They describe the device as a 360-degree-viewable volumetric 3-D display with a resolution of 768 x 768 x 198 and a 24 Hz volume refresh rate. The apparatus contains an embedded graphics processing system, and uses dithering methods to create images of 3-bit to 21-bit-stippled color, which is perceived as several hundred colors. How much is it? I couldn't find a price on their website, but I did find it in this UK-based site: $80738.95. Ouch, though if you are one of the first 50 buyers, they'll give you a free Dell PC worth $2200. Whoo-hoo. Here's the datasheet. They offer their patents for licensing.
I found the price, it is in their powerpoint slides: ~$40K. Oh, also hidden in there, they now have $11M in funding and about a dozen very high end clients.