1. A method performed by a mobile device, comprising: receiving a request to perform a task, the request specifying that the mobile device shall perform the task when the mobile device is located in a specified geographic region; determining a first code division multiple access (CDMA) location of the mobile device using a first CDMA identifier, the first CDMA identifier being associated with the first CDMA location; determining that the first CDMA location intersects the specified geographic region; upon determining that the first CDMA location intersects the specified geographic region, determining a second CDMA location of the mobile device using a second CDMA identifier, the second CDMA identifier being associated with the second CDMA location, the second CDMA location having finer granularity than that of the first CDMA location; and performing the task upon determining that the second CDMA location of the mobile device intersects the specified geographic region.