A environmental sensor network having at least two environmental sensor units and a central display unit. Each sensor unit includes a sensor adapted to measure a condition and a transmitter adapted to operate in an "activation" mode in which the transmitter transmits a predefined sequence and a sensor ID and a "data" mode in which the transmitter transmits data based on the measurement. The central display unit includes a receiver adapted to receive a transmission from the two environmental sensors, a memory device, and a processor adapted to selectively operate in an "add" mode in which the processor records the presence of an environment sensor unit in the memory device upon the receipt of the predefined sequence and the sensor ID, and a "display" mode in which the processor outputs information based on the measurement.