Microsoft released 2 days ago the Touchless SDK multi-touch technology. This basically means that developers will have the possibility of building multi-touch applications using a webcam and a color marker. Utilizing the webcam, applications can track the location and size of the color marker to enable multi-touch functionality without touching a surface, as stated by Microsoft.
You can develop either applications or games using the Touchless SDK, just let your imagination flow. Broswing through your media using the Touchless SDK will be alot more “fun” now and without the need to expensive hardware, a webcam is all you need. For a more acurate impression, you can see a quick demo of this technology here.
Also, as a developer you can contribute to the Touchless code, present on Microsoft’s CodePlex website