With Satellite Phones you can keep in touch on a global scope with voice services and, with some models of satellite phones, you may even use data services as well. Satellite HotSpots bounce signals off satellites allowing you to keep connected on a global scope; with some you even have global pole-to-pole coverage.
With this type of coverage it does not matter if you are within the reach of cell towers. Even during a complete outage caused from a natural disaster where all other communication mediums are down your satellite phone will continue to keep you connected. This makes satellite phones perfect for something as simple as staying connected while off the grid or something much more important like a critical lifeline. Some are even specifically engineered with functions to make sure you get help as fast as possible.