An electronic lockbox sends identifying data to a portable communications device, which relays that data to a central computer, generating a response from the central computer containing customized information of special interest to the user. Such data can include information relating to the lockbox's property, and contextually relevant information relating to other similar properties nearby. Such data from the central computer also can be delivered to one more auxiliary portable communication devices, including such devices carried by individuals either in close proximity to the lockbox or at a remote location. The data also could comprise visitation history relevant to the user, allowing an agent or a prospect to review information about previous visits to properties. The central computer can also query a user to provide location information for a lockbox that has been added to the system database.