This is a working proof of concept written in Perl that will allow one to unlock their XScreensaver with an RFID card. Put an RFID card in your cellphone case or on a keychain and hide the reader under your desk. When you return, the program will type your password and unlock the screensaver. Touted as "cute" and not the correct way to do things from the XScreensaver author himself, use this at your own risk. http://hackaday.com/2013/09/07/hidden-rfid-reader-locks-workstation-unless-keys-are-present