I solder the Velleman K8019 kit together and made my own software:

And now let the creative thought flow!
Make a more complex program ^_^

This is a screen of the official Velleman program:

Its used to program the RFID reader you can change the door open system and add or remove cards from the system.

If you write your own program you can gather the data from the serial port and make your own database and give it functions.
For now I don´t have the need for the door unlock feature but its handy for future project.
Example : Turn on pc by presenting rfid card