I use an electric door strike, on Smarthab, it is relay controlled via 24VAC from the room controller.
The room controller is a TI C3200 LaunchPad, this gives me ethernet access so there is no money wasted. The room controller talks to an external keypad with an RFID receiver installed as well. This can be coupled to the room controller for simplicity or directly controlled with an Arduino which would communicate to the room controller via RS-485.
The decision to open the door or not is handled back at the server running Linux and MySQL.
The code for the TI Launchpad is written in C. while the Arduino uses its IDE.
The door keypad also has a small LCD display for displaying messages, which are canned, as well as messages from the server. Such as a two-part message:
Access Granted: canned
<name> : from the server
The system also logs the time when people enter and leave and in idle mode just displays the date and time, which comes from the server via SNTP server.
The demo will be on my desk and since the door strikes are over $100 US I will just be lighting a LED.