Thermostat 110 can be one of several thermostats that may control HVAC system 120. Thermostat 110 can be referred to as the “primary” thermostat because it may be electrically connected to actuate all or part of an HVAC system, by virtue of an electrical connection to HVAC control wires (e.g. W, G, Y, etc.) leading to HVAC system 120. Thermostat 110 can include one or more sensors to gather data from the environment associated with enclosure 100. For example, a sensor may be used to detect occupancy, temperature, light and other environmental conditions within enclosure 100. Remote thermostat 112 can be referred to as an “auxiliary” thermostat because it may not be electrically connected to actuate HVAC system 120, but it too may include one or more sensors to gather data from the environment associated with enclosure 100 and can transmit data to thermostat 110 via a wired or wireless link. For example, thermostat 112 can wirelessly communicate with and cooperates with thermostat 110 for improved control of HVAC system 120. Thermostat 112 can provide additional temperature data indicative of its location within enclosure 100, provide additional occupancy information, or provide another user interface for the user (e.g., to adjust a temperature setpoint).