This system is so dependable that it is used by the United States Department of Defense. This is because they have proven their reliability in even the worst and most barren of conditions. Iridium satellite phones allow worldwide voice and data communications using handheld devices. The system is amazing, as someone from the North Pole could call someone lost in the middle of an Australian outback. The coverage literally includes the entire world, though there are some areas where the system is not allowed to be used, usually in nations that the United States has an embargo on (such as North Korea and Sudan). Many of the satellites seen in the night sky that give short bright flashes belong to the Irdidium system.