The work presented in this thesis has two distinct parts:​ (i) development of a spinal motion measurement technique and (ii) incorporation of the spinal motion measurement with galvanic vestibular stimulation (GVS) technology, acting as a balance assist device hereafter referred to as a galvanic vestibular stimulation device (GVSD). The developed spinal motion measurement technique fulfills seven desired attributes:​ accuracy, portability, real-time data capture of dynamic data, non-invasive, small device footprint, clinically useful and of non-prohibitive cost. Applications of the proposed system range from diagnosis of spine injury to postural and balance monitoring, on-field as well as in the lab setting. The system is comprised of three inertial measurement sensors, respectively attached and calibrated to the head, torso and hips, based on the subject’s anatomical planes. Sensor output is transformed into meaningful clinical parameters of rotation, flexion-extension and lateral bending of each body segment with respect to a global reference space, then collected and visualized via an interactive graphical user interface (GUI). The accuracy of the proposed sensing system has been successfully verified with subject trials using a VICON optical motion measurement system. Next, the proposed motion measurement system and technique has been used to record a standing subject’s motion response to GVS. The data obtained allows the development of a new GVSD with the attributes of:​ eligibility for commercial licensing, portability, and capable of safely providing controlled stimulating current to the mastoid bones at varying levels and frequencies. The successful combination of the spinal motion measurement technique and GVSD represents the preliminary stage of a balance prosthesis.