A low cost, robust, repeater for a wireless ambient sensor system that provides an extended period of operability without maintenance is described. The repeater includes a controller and first and second transceivers. The controller is configured to control operation of said first transceiver and said second transceiver. The wireless repeater includes a repeater identification. The controller is configured to manage a sensor unit identification table that contains a list of sensor unit identification codes, where entries for the sensor unit identification table are received by the second transceiver from the base unit and identified by the repeater identification. The controller controls the first transceiver and the second transceiver to forward data from sensor units listed in said sensor unit identification table and to ignore data from sensor units not listed in said sensor unit identification table. The controller also controls the first transceiver and the second transceiver to forward data from the base unit that is addressed to sensor units listed in said sensor unit identification table and to ignore data from the base unit that is addressed to sensor units not listed in said sensor unit identification table. The controller places the first transceiver and the second transceiver in a low-power mode when no transmissions are expected from the base unit or from the sensor units listed in the sensor identification table.