This is my el-cheapo DIY multi-touch interface in progress. So far, it's just the display half of the project. I've taken an old overhead projector and laid it on it's back pointing up through a piece of glass onto some typing paper. There is an lcd overhead panel displaying a crude smiley made with a monome and this is rear-projected onto the paper. It's high noon with the shades drawn.
What's kind of amazing is that I took no measurements and just sort of laid the stuff out to see what sort of structure I'll have to build, and yet it already almost works well enough. Though blurry, this sort of resolution (big blobs of color) is plenty for most preliminary audio/display apps I can think of. Adjusting (raising) the table height will get the diffusor into a better plane for this projector and result in a much crisper image. It'll help when the sun goes down, too.
Next I'm going to try the infrared blast approach to generating the finger touch blobs, using a budget night-vision security camera.
more pics
