While writing my Silverlight wish list I found a very nice project. Johnny Ching Lee is using the controller (Wiimote) of the Nintendo Wii to track fingers. The controller does not need the Nintendo Wii console, simple the controller and a bluetooth connection is enough. Combining this project with WPF or Silverlight would be the answer of one of my wishes. (Well, I know what I will try during the holidays.)
While searching the Internet I found a managed library for Nintendo's Wiimote. The source code for this library is available at codeplex.com.
Other Finger Tracking Systems
In the following short video Michael Dell shows the new Dell Latitude XT which has multi-touch capabilities. I'm very tight if this type of Tablet PC will be available next to buy. I will be one of the first, sure.
Another project is the Microsoft Surface table which is currently not available in Europe. The Surface team has a new blog where you can read about the latest news.
I just got a Wii so I'm setting up a 8' x 6' whiteboard in my office now ;)
It works great ! The most diffucult part is to find a shop in the Real World where you can buy the LED IR.
funny, I was thinking of doing the same during the hollidays. Have you looked at the touchlib library. (code.google.com/.../touchlib) Might be useful.