1. A wireless programmable digital thermostat system comprising: a plurality of portable, hand-held transmitter units adapted to transmit input signals over a wireless communication medium, each of the transmitters including a user input mechanism adapted to receive programming inputs from users of the transmitter units, each of the transmitters being adapted to generated the input signals in response to the programming inputs, each of the transmitters further including a display adapted to display indicia of the programming inputs; and a receiver unit for a thermostat system which includes a plurality of environmental control apparatuses, the receiver unit including a controller adapted to be programmable in response to the input signals according to a plurality of programming modes and to generate and provide control signals to the environmental control apparatuses, the controller being adapted to facilitate automatic adjustments in control variables associated with at least one of the programming modes, the controller being adapted to process the input signals to identify a transmitter unit which has most recently received a programming input and to control the thermostat system only in response to input signals received from the transmitter unit which has most recently received a programming input.