This disclosure relates to a mobile device that is suitable for detect geofence crossing events. In some instances, the mobile device can detect geofence crossing events using a lower power algorithm or a higher power algorithm. The mobile device may allow a user of the mobile device to specify whether a lower power algorithm or a higher power algorithm is to be used when detecting geofence crossing events. In some instances, the mobile device may automatically change from a lower power algorithm to a higher power algorithm if a predetermined abnormality is found to be present in the detected geofence crossing events. In some instances, the user may be prompted to confirm automatically changing from a lower power algorithm to a higher power algorithm if a predetermined abnormality is found to be present in the detected geofence crossing events.