Techniques, methods, systems, devices, and computer readable medium are disclosed from an oral cavity of a user identifying a feature in the user's oral cavity, tracking the feature as it changes, and determining a condition based on the tracking of the feature in the user's oral cavity. The user can use an interface provided by the device's user interface for activities such as biofeedback, controlling functions of the device and other devices, receiving information from external devices or the device, etc.