A sensor system is mounted on a host for recording motion of the host over time. The sensor system includes a sensor pad having a surface with a positive slope away from a center of the surface, and a mass resting on the sensor pad. The sensor pad includes an array of pressure sensors for determining the location of the mass on the sensor pad. The sensor system can further include a memory and a controller coupled to the memory and the sensor pad. The controller can determine the motion of the host from the location of the mass and record the motion in the memory.