Splitwise - Splitwise is a free tool for friends and roommates to track bills and other shared expenses, so that everyone gets paid back. On the web, iPhone, and Android!

Face++ - API for face detection – also detects gender, age, pose

Dinngo - Splitting payments the fun and easy way

Facesoft - The world's most accurate face recognition algorithm

/Tab - The simple way to split a bill among friends.

Facial Recognition by FB - Get notified if someone tries to use your photo on Facebook