1. A method for controlling a heating, ventilation, air conditioning (HVAC) system, comprising the steps: determining a travel time from each of a plurality of mobile sites to a fixed site; determining a conditioning time for a HVAC system at the fixed site; turning the HVAC system ON when any of the travel times is less than the conditioning time; turning the HVAC system OFF when all of the travel times are greater than the conditioning time plus a threshold time, wherein the conditioning time is determined using a building thermal model, and wherein the steps are performed in a processor; wherein each mobile site communicates a separate travel time to the fixed site; wherein the fixed site calculates a separate conditioning time, and the HVAC system uses separate threshold times for occupants sharing a same environment; and wherein each mobile site includes a mobile transceiver and a mobile locator, and wherein the fixed site includes the processor and a fixed transceiver for communicating with each mobile site via a network.