Another approach is to use a projector onto a desktop; doing the geometric
correction for off access projection is pretty easy, and you can project
onto any surface.

One wonderful demo in the MIT media lab is the idea of board games on the floor
with your kids, with no pieces to pick up afterward :-).

What is more, the cost of projectors is coming well down with time....
Should be in the $1k range within a year or three...
                         - Jim

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Jim Gettys
Cambridge Research Laboratory
HP Labs, Hewlett-Packard Company
Jim.Gettys at hp.com