In the fall of 2007 a YouTube clip by Johnny Lee got people excited about building a cheap version of an interactive Whiteboard by using a Wii remote controller and an infrared pen.
http://www.youtube.com/watch?v=5s5EvhHy7eQ
His website describes how to make this. There is a schematic for creating the infrared pen.
http://www.cs.cmu.edu/ johnny/projects/wii/pen.jpg
Since that time various sites have documented different ways to make the pen and there has been development on software that will run the whole thing. On the Mac side of things Uwe Schmidt has done an admirable job of writing, testing, updating and documenting software.
http://www.uweschmidt.org/wiimote-whiteboard
His site also contains a Blog where suggestions and solutions to problems are posted.
For those who use Windows XP or Vista, Boon Jin has developed software that has been reported as very successful. Wiimote Smooth Board 0.2 BETA
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