|Source Facebook Newsroom|
Facebook created a tool that works on smartphones (Android, iPhone), feature phones and on your PC. If you are in an area where a major disaster strike you will receive a notification from Facebook. The message will me something like: Are you OK? It looks like you're in the area affected by an earthquake. Let friends know if you're safe.
You have two options: I'm Safe or I'm not in the area. This update will generate a post in your timeline and every of your friends can see it.
If some of your friends are in such area you will have the option to see the list of your friends and how many of them are in safe.
Here is a video that shows how it works:
Introducing Safety Check from Facebook on Vimeo.