I built on Kyle McDonald and Arturo Castro's face substitution work by creating a simple mesh editor. This lets you tweak how the texture is applied to your face so you can use images where the face isn't detected properly. It also means you can swap your face out for non-faces.
Demo video http://vimeo.com/54324560
Jason Saragih's FaceTracker library http://web.mac.com/jsaragih/FaceTracker/FaceTracker.html
Kyle McDonald's ofxFaceTracker addon http://github.com/kylemcdonald/ofxFaceTracker
Kyle's face substitution demo http://vimeo.com/29348533