The Distance Filter only shows objects within a distance range, for instance all objects that are between 100 cm and 200 cm away from the Kinect.
It can be used as a different way for green (blue) screen techniques and background subtraction techniques.
For determining the distance per pixel the kinect.depthMap is used.
NEW, UPDATED VERSION (16-07-2013)
Far better performance because of a better and faster blur filter and several other improvements.
Get the source code HERE and have fun!