Techniques of non-intrusive region notification are described. A mobile device can be programmed to trigger an application program when the mobile device enters or exits a region. The region can be defined by various virtual fencing technologies. If, at the time of entry or exit of a region, the mobile device is in a power-saving operating mode, the mobile device can transition to an active operating mode temporarily, register a fence-crossing event (entry or exit of the region) with the application program, and then transition back to the power-saving operating mode. The mobile device can launch the registered application program in response to the mobile device receiving a user input to enter the active operating mode. The application program can provide a user interface associated with the region on a display surface of the mobile device in place of a home screen or other user interface.