Apple was recently granted a patent on monitoring cellular network conditions to help identify network dead spots. U.S.
Patent No. 8,886,178 describes a “Location-based profile” designed to help cellular carriers and device makers collect crowdsourced information on localized areas where network problems such as dropped calls occur.
The patent describes using device-based location services to allow individual iOS devices to automatically provide monitoring data to server-side systems. The tool would likely act as a background task using geofencing to relate it to known coordinates of surrounding cellular towers and trigger mobile monitoring systems on that basis to collect more detailed data when a known dead spot is encountered.