Mobile device system including sub-application that executes in response to host application execution

A mobile computing device system, comprising:

• a first host application on a mobile computing device;
• a global positioning system (GPS) on the mobile computing device;
• a sub-application on the mobile computing device, the sub-application configured to selectively execute in response to execution of the first host application by the mobile computing device;
• a first user interface displayed by the first host application on the mobile computing device by the first host application;
• wherein the sub-application is configured to execute a method including:
• determining a location of the mobile computing device by the GPS;
• and
• if the mobile computing device is determined to be at a location within a predetermined geographic area, then generating an alert message including digital content associated with the first geographic area, and displaying the alert message on the first user interface;
• and
• if the mobile computing device is not determined to be at a location within the predetermined first geographic area, then not displaying the alert message on the first user interface.