US Patent 7620001 Communication system and method with mobile devices

A system comprises a plurality of mobile devices each operable to communicate via a computer network, a gateway operable to communicate with the plurality of mobile devices via the computer network, and a database coupled to the gateway. The plurality of mobile devices are each operable to periodically transmit a heartbeat message to the gateway, where the heartbeat message includes an address and a device identifier of the mobile device. The gateway is operable to store the address and device identifier in the database and send an acknowledgement message in response to each received heartbeat message.