A computer-implemented method, including detecting, by a first client device, a presence of a mobile customer in a particular geographic location, with detecting being through a direct device communication between the first client device and a second client device that is associated with the mobile customer; in response to the mobile customer presence detection, updating a local registry of the first client device with a customer identifier of the mobile customer; and retrieving, from a server device, customer information about the mobile customer; generating, based on contents of the local registry, a list of customers who are presently located in the particular geographic location; and rendering on a display device of the first client device at least one of the list of customers or the retrieved customer information.