Satellite phones are a technology proven to facilitate communications in remote destinations, making sat phones ideal for wilderness adventure seekers, sailors, or teams responsible for emergency preparedness and contingency planning. 

Satellite phones offer call and SMS text messaging communication services and low-bandwidth internet access are supported through most systems. They do not route calls through land-based cellular towers like traditional mobile phones; rather, they transmit data through satellites orbiting the planet. This network of satellites is either “fixed above the Equator (geostationary), or in Low Earth Orbit (LEO) anywhere from 500 to 1,000 miles above the earth.” Satellite phones are therefore not reliant on cell towers that can be damaged by natural disasters or may be non-existent in remote locations. Due to the satellite architecture, these phones can essentially work anywhere in the world, greatly assisting organizations operating in locations that lack a reliable communications infrastructure. Minutes can be prepaid or bought via monthly airtime contract, and are often categorized as less expensive than foreign roaming charges on a typical cell network.

Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions.

However, satellite phones are also not advocated as a replacement for cell phones, as they have been criticized as bulky and cumbersome. They do not consistently offer the day-to-day Internet access of today’s smart phones. Additionally, satellite phones typically require an unobstructed view of the sky in order to operate effectively. This can hinder connections from the interior of buildings or vehicles, areas close to tall buildings or dense vegetation, and in deep valleys or canyons. Nonetheless, satellite phones are still considered a useful tool for communicating in remote areas.

A fixed installation, such as one used aboard a ship, may include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that automatically tracks the overhead satellites. Smaller installations using VoIP over a two-way satellite broadband service such as BGAN or VSAT bring the costs within the reach of leisure vessel owners. Internet service satellite phones have notoriously poor reception indoors, though it may be possible to get a consistent signal near a window or in the top floor of a building if the roof is sufficiently thin. The phones have connectors for external antennas that can be installed in vehicles and buildings. 

- Credit: Wikipedia.org, US Dept. of State

There are four satellite phone network providers, Iridium, Inmarsat, Globalstar and Thuraya.