The electronics are so compact they can easily fit into a hand held unit, a cell phone, a lap top, an automobile, a boat, wrist-mounted compass etc. Some units have Bluetooth connectivity. Some have built in maps of entire continents so they can display where you are or direct you to where you want to go by roads. Some speak. Some take voice input.

The GPS scheme was originally developed by the US military for use in guiding weaponry. At first they hobbled its accuracy for civilian use, then dropped that on the understanding they might shut the system down at any time that they felt the GPS system might be used for military purposes against US interests. The military then built an even more accurate system strictly for military use.

Spot is a two-way GPS service that sends your location to a satellite where it can be relayed to 911 emergency service or your friends. It costs $170.00 USD for the unit and $8.50 USD a month.