If you're looking for the status of friends who might be in Paris, head to the Safety Check page on your Facebook account. The page will list your friends who last checked in around Paris and give you a running tally of who is marked safe.
People who are in Paris can either mark themselves safe or be marked safe by another friend, and the update is added to their Facebook feed.
In addition to the check-in process, the Safety Check page allows you to subscribe to notifications, which will alert you as your friends check in. Obviously not everyone knows about this feature but the service seems like a smart way to keep track of people and communicate with travel restricted and a state of emergency declared.