As part of my Masters in Arts Computing at Goldsmiths College, London in 2004/05, I developed an application which utilized a TV capture card to overlay in real-time subtitles of other media or doodled moustaches and glasses over the faces of people who appeared on TV, thereby subverting the meaning of the pictures and so interrupting the expectations of the spectator for a medium that is taken so much for granted. The system utilized the openCV computer vision library to automatically detect the people's faces that appeared on TV. The application was shown as part of the .node London Digital Arts Festival in March 2006.
Please visit the project's website for more information