Sren Louv-Jansen developed a tool that enables you to track the sleeping habits of your friends on Facebook. The tool is available on his Github page, available on the site. Facebook says the tool violates its terms and conditions and should not encourage anyone to use it. The developer has since stopped using the tool, but has refused to take it down from GitHub. He hopes the tool will educate users about the privacy implications of their digital lives and encourage them to take action to make sure they know what information is being collected about them.”]
Source: https://grahamcluley.com/track-facebook-friends-sleeping-habits/