Abstract: A message targeting system enables content providers to define geophysical zones for which entering mobile electronic devices may receive messages. The targeting system catalogs messaging campaigns for client defined zones and stores them in a database. An exchange identifies mobile devices for targeting and auctions available display space thereon, providing the targeting system with geolocation and other device-specific data. The targeting system contrasts device geolocation data to client created zones to identify qualifying campaigns, selects one and issues its bid. If the targeting system wins the bid, the exchange transmits its contact information to the mobile device to enable it to contact the targeting system. If the device does so, the targeting system transmits the message to the device directly, even if the device has left the zone.