Abstract: This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media for supporting communication between a first device, such as a smartphone, and a second device, such as a smart thermostat associated with a heating, ventilating, and air conditioning (HVAC) system. In one aspect, a smartphone with a temperature sensor can detect a local environment temperature and communicate with the smart thermostat to turn on/off various HVAC modules to adjust the temperature in that local environment. In some implementations, a first smartphone can be used to detect the temperature in a first room and communicate with the smart thermostat to turn on/off various HVAC modules in the first room, and a second smartphone can be used to detect another temperature in a second room and communicate with the smart thermostat to turn on/off various HVAC modules in the second room.