Heating, ventilation and cooling (HVAC) consumes nearly 50% of electrical energy spent in homes and offices worldwide. To adapt an HVAC system to the dynamic environment and save energy without compromising the comfort level of the occupants, different techniques have been explored to sense the real-time occupancy in rooms, zones and buildings. Among all these approaches, wireless camera-based sensing is appealing for its intrinsic application potentials in surveillance and security besides energy management. However, limited life-time and detection accuracy, due to embedded energy storage and computation capability constraints, have prevented pervasiveness of wireless camera-based occupancy detection. This paper presents a novel wireless device platform and prototype development that incorporates IR camera with optical camera to provide collaborative intelligence at low-power and high-accuracy. Compared to an optical camera based baseline design, we demonstrate 65 χ improvement in miss rate, 5 χ reduction in detection false positive rate and 25% lifetime extension for battery usage; and a maximum of 40% HVAC energy savings compared to thermostat based control.