While a little late, here are is the source code and the slide deck for my recent talk at the Twin Cities Silverlight User Group.

SLMotionDetector.zip

This includes a solution with the source code for the common MotionDetection library, a silverlight application with OOB capabilities, a Windows Phone 7 app and a failed WPF attempt.

You will need the Windows Phone 7 Mango Beta 2 SDK to run the WP7 project. This does include compiled versions of the NESL libraries. The source can be found at http://archive.msdn.microsoft.com/nesl/Release/ProjectReleases.aspx?ReleaseId=5519

This code is provided as-is. It comes with no support and complete with "Works on My Machine" credentials. I have removed the certificates used for signing the libraries, you may need to create your own to run the app out of browser. I have not taken the time to clean up the code or remove commented out old code..