Face Detection in JavaScript with getUserMedia
Adapted to work with the getUserMedia API using code from github.com/wesbos/HTML5-Face-Detection
Try out the demo using Google Chrome with the "MediaStream" flag enabled in about:flags
Note that this demo only works online (or localhost) due to security restrictions. It won't work on a local file:/// system!
Also recommended is headtrackr which is a more sophisticated face- and head-tracking JavaScript library.