Saint Louis-based biometrics startup FacetoFace has filed a patent for a facial recognition-based security app designed for use with messaging services on devices.The new patent environs a system where facial recognition is not just used for security on a phone's messaging service, but also for reading facial expressions.The benefits of added expression recognition are added potential for gesture control, and “the creation of a stimulus response database for advertisers”.FacetoFace has developed a messaging security solution continuously monitors a user's face when they are using a service.If the phone cannot “see” the right user's face, and another person takes the phone, then the message text is obscured.