A system includes fobs and sensors each of which has a wireless transceiver, a processor and a battery powering the transceiver and processor. A server includes a processor and wireless transceiver, both of which are mains-powered. A fob processor timer repetitively causes its processor to enter a normal mode from a sleep mode, cause the transceiver to enter a powered state from a reduced power state, and send a wireless message from its transceiver to the server transceiver to request data therefrom. A sensor processor timer repetitively causes its processor to enter a normal mode from a sleep mode, cause the transceiver to enter a powered state from a reduced power state, read an analog or digital input, and send a wireless message based upon the read input from its transceiver to the server transceiver to provide data thereto. Each of the timers times asynchronously with respect to other timers.