This video shows an alternative way of creating interactive surfaces (such as an electronic whiteboard), using infra-red detection. This has been tried several times before, there is actually a (Chinese) interactive whiteboard product on the market that uses this principle. Typical issue is the blocking of the IR signal by the user. Also, tracking speed and accuracy are challanges. Here is a link to the Author’s blog where you can download the code.
Low-Cost Multi-touch Whiteboard using the Wii Remote