At BETT there were several companies demonstrating projectors that had their own built-in system for detecting a pen, giving the same functionality of an interactive whiteboard, without the whiteboard bit.
Epson were demonstrating their 450i Model (click for specs) which looked pretty interesting. I had a play with it on the stand and it seemed pretty responsive. It’s also a very short throw projector so it casts less of a shadow as it’s mounted directly above the board.
This projector means that any piece of wall could be used as an interactive surface.
Like many cheaper IWB solutions it suffers with the software that’s bundled with it. The Epson was was pretty limited – write on board, basic shapes, whole screen capture (but not area). You’d need to get hold of third party software to do anything more than present with it – but it’s certainly a game-changer. Pricewise it works out cheaper than a projector + whiteboard solution.
Definitely a technology that’s worth keeping an eye on.