ofxFaceTracker is openFrameworks addon is based on Jason Saragih's FaceTracker library.
openFrameworks is an open source toolkit for creative coding.
FaceTracker is open source for non-commercial use, and is available from Jason directly. One you have Jason's source, you'll need to drop it in libs/ (e.g., libs/Tracker/Tracker.h). You'll also need to drop the model data in bin/data/model/.
If you would like to prototype an idea involving face tracking, I encourage you to download FaceOSC.
Provides a minimal example of using an ofxVideoGrabber with an ofxFaceTracker, then extracts and draws the ofPolyline representing the left and right eyes.
Demonstrates how to get the image-space position of the face, and the 3d orientation (collectively, the face "pose") then applies these to the OpenGL context in order to draw an oriented face mesh.
Demonstrates how to use the mean face mesh to draw pose and expression normalized representation of the face currently being tracked.
Demonstrates the ExpressionClassifier, which can load, save, and classify expressions into pre-trained categories. Provides basic expressions (eyebrows raised, neutral, smiling) as examples.
Fairly complicated example that demonstrates some advanced/experimental features of ofxCv and ofxFaceTracker for doing AR-style augmentation of the face.
Sends as much data as possible from ofxFaceTracker via OSC, including various "gestures", position, and orientation.