Systems and methods for recognizing motion made by a moving person are presented. The system includes a thermal sensor configured to generate a low frequency or direct current signal upon receiving thermal energy. A spatially modulating optic is disposed between the thermal sensor and the warm object. The optic is configured to modulate the thermal energy received by the thermal sensor as a function of an orientation of the moving person with respect to the thermal sensor. An electronics unit in communication with the thermal sensor includes a memory and a processor. The processor is configured by the memory to detect a change in the thermal sensor signal and recognize a characteristic of the thermal sensor signal.