LipPass is a user verification system for mobile devices that verifies your identity by the unique way that you move your lips. Developed by researchers at Shanghai Jiao Tong University, the system doesn't validate based on the sound of your voice but rather the movement of your mouth. From IEEE Spectrum:
The researchers realized the audio components on smartphones can be exploited to depict the movement of a person’s mouth by analyzing the acoustic signals that bounce off the user’s face. Since each person exhibits unique speaking behaviors—like lip protrusion and closure, tongue stretch and constriction, as well as jaw angle changes—this creates a unique Doppler effect profile that can be detected by the phone. The platform then uses a deep learning algorithm, which extracts distinct features from of the user’s Doppler profile as he or she speaks. Next, a binary tree-based approach is applied to distinguish the new user’s profile from previously registered users, which also helps discriminate between the identity of legal users and spoofers...
In a controlled laboratory environment, LipPass achieved an overall authentication accuracy of 95.3 percent... Across all environments and all kinds of attacks, the overall (spoof) success rate was less than 10 percent, though attacks that used the third method—a recording of the user's Doppler profile—did succeed nearly 20 percent of the time under controlled, laboratory conditions.
"Lip Reading-Based User Authentication Through Acoustic Sensing on Smartphones" (IEEE/ACM Transactions on Networking)