What is it?
The app's page describes the Get Friend Map as: "View your friends connection around the world on a beautiful map." (Note: the app creator's English is quite broken, so to save time, I'll just leave out all the sic notations.)
In order to accomplish this, the Get Friend Map collects location data from your friends' profiles and uses a representative glowing dot on a very dark world map to show the far-flung nature of your social network.
How Accurate is it?
It's as accurate as your Facebook friends are honest. If they aren't lying about their location--such as my friend who claims to reside in but who actually lives in a weird-smelling studio apartment in Boston--the dots on the Get Friend Map appear to be accurate.