Wikipedia
Pfinder
Pfinder is a computer vision system which detects features in video images in order to recognize human figures and their movements and gestures. Pfinder was designed by Wren, et al. of the MIT Media Laboratory in 1997. As described by its authors, Pfinder is a "real-time system for tracking people and interpreting their behavior". The system improves upon previous works by not only identifying the boundaries of a person in the image, but also analyzing the regions inside the boundaries and relating them to the known structure of the human body. As an example, Pfinder can track a person's head and hands, and can determine the pose of the body and recognize gestures.