Jack's detailed human model can be driven by external sensors in real time [3]. Using as few as 4 Ascension Technology Flock of Birds 6-DOF sensors we are able to create a good approximation of a human operator's posture. By using both specific computational models of body sections (e.g the spine) and a general inverse kinematics algorithm we can achieve a high degree of realism while minimally encumbering the operator. This allows more natural movement with fewer distractions and encumbrances than existing systems.