Methods and apparatus for controlling an external device via at least one signal modulated by movements of a user's tongue, maxillaries and lips may include a mouthpiece comprising a controller and at least one signal emitter and one signal detector. A signal generated by the at least one emitter may be modulated by changes to the geometry of a user's oral cavity and detected by at least one signal detector. The at least one detected signal may be processed by a controller and transmitted to a remote device in order to provide control capability made possible by the degrees of freedom available by manipulation of the geometry of the user's oral cavity.