By using the very simple and cheap PIC Microchip micro-controller it's possible to generate signals. With these signals you can display all kinds of pixel patterns on any VGA monitor or beamer. During the workshop participants will create their own "VGA test box" that will make it possible for you to do the same.
I have been experimenting today with controlling the RGB lines of a VGA connection on a computer monitor using Arduino. The results have been quite promising -- in fact, it was very easy to do and the outcome was considerably better than i had anticipated.
For sending and receiving messages in Flash, you could use the pretty expensive Flash Communication Server / Flash Media Server, or you could use a simple socket server, such as this one, written in Python. Feel free to download it and set it up.