Goal:
 - Card is read
 - UID is piped to door-key-bubble-jet-printer-daemon
 - door-key-bubble-jet-printer-daemon (dkbjpd) toggles open/close
 - it works

Features:
 - opening/closing of key is logged
 - state of key is periodically checked and logged
 - open/close toggling can be triggered by different sources, like
   - RFID card
   - phone calls
   - agressively watching onto a Windows login screen
 - learn-mode
   - simple way to add new rfid cards to allowed card-list

Architecture:
 - door-key-bubble-jet-printer-daemon
   - can open/close door
   - logs state of door
 - rfid-reader
   - recognizes presence of accepted rfid-card and toggles door
 - voip-reader
   - recognizes phone call of accepted caller-id and toggles doort
 - door-key-ubble-jet-printer
   - accepts single-character commands and writes
     success and status messages
 - *-reader write to a fifo, which is listened by the
   door-key-bubble-jet-printer-daemon
 - rfid-learner

Design:
 - Perl is great for everything.
 - Shell is for the rest.