I came across this InfoWorld news article today on an open source SDK for creating multi-touch based applications using a webcam for input.
Wouldn't it be cool to have this kind of application to work on your mobile phone with the built-in camera?
I have played a couple of proprietary games on the mobile phone that have this kind of capability, it's nice that Microsoft CodePlex is making touchless SDK accessible to the masses.
Get the SDK here: www.codeplex.com/touchless