A wireless communications system includes a wireless communications network and a plurality of wireless communications devices. The wireless communications devices are each configured to communicate via the wireless communications network. At least one of the plurality of wireless communications devices has a portable housing, a wireless transceiver carried by the portable housing, and a wireless-based, availability detector carried by the portable housing. A processor is carried by the portable housing and is configured to determine a first availability status based upon the NFC device at a first time. The processor is further configured to activate the wireless-based, availability detector based upon the NFC device to thereby determine a second availability status based upon the wireless-based, availability detector at a second time after the first time. The processor is additionally configured to communicate the first and second availability status to the wireless communications network via the wireless transceiver.