Yes, it is possible with the help of CLLocationManager startMonitoringForRegion which will call your application when entering / exiting a certain "fenced" geolocation.
BUT , since the user's location will / will be used, the location icon will appear until this call is canceled (using the appropriate stopMonitoringForRegion)
(on iOS6, this icon will be replaced by a different location icon for the "regional" location instead of the usual use of the location - it looks like the outline of the current icon)