builds a model of background using GMMs (builds on an implementation by Zivokic, 2005), uses this model in finding foreground elements, and visualizes them using openFrameworks (very nice code by stefanix), and tracks orientation using the leading motion vector (using opencv's lucas kanade optical flow)
pkmital/pkmBlobTracker
Background modeling for foreground subtraction, tracks multiple blobs (people), their orientations (using leading motion vector), and has a nice visual display for seeing the results... video demonstration here: http://vimeo.com/22054133 - more info here: http://pkmital.com
C