Android app on face detection/recognition. It uses the Java wrapping of the popular machine learning OpenCV library -> JavaCV to create an android application. It has the 3 popular algorithms (Eigenface, Fisherface, LBP) along with the changeable parameters using which face recognition can be carried out.
NOTE: On the issues - recent changes to Android OS and permission means this will no longer work without reworking the permission in the app. The core machine-learning features are still valid though and can be ported over to a modern android app.