A vestibular prosthesis system is described which includes an external movement sensor that is attachable a patient's head for generating an external movement signal. A fail-safe sensor is configured to detect movement of the one or more external movement sensors relative to the head and generate a corresponding relative motion signal. And an implant processor also is implantable under the skin and in communication with the fail-safe sensor and the external transmitter for generating an implant stimulation signal based on the external movement signal and/or the relative motion signal to electrically stimulate target neural tissue for vestibular sensation by the patient.
