This is a sample of implementing the Emgu libraries with a XNA game.
I use Emgu to show the video of a web cam as the background of the game
while using the HaarCascade's algorithm to detect the faces that appear in the camera stream.

My blog post - http://bettercoderwannabe.blogspot.it/2012/10/a-face-tracking-sample-with-xna-and-emgu.html

The Emgu libraries - http://www.emgu.com/wiki/index.php/Main_Page