The tool, named “Safety Check,” will soon be available globally to over 1.32 billion Facebook users. The tool is designed to be activated after a natural disaster and by using either the city you lived in or your last location – if you have checked in on “Nearby Friends”, it let’s you alert your friends and family that you are safe, while also tracking the status of others. According to Facebook, this new move is in the wake of 2011 earthquake and tsunami disaster in Japan.
Source: https://thehackernews.com/2014/10/facebook-safety-check-allows-you-to_16.html