When I started writing the brew-controller I used 2 raspberry pi's to scale up the number of GPIO pins. This was before I'd started to use I2C controllers to expand the GPIO capabilities. As a result of this I had used multicast to provide communication between a master and slave.
This intercommunication with multicast really means it's easy to broadcast state onto the network. It has been fairly trivial to start an Android application which displays what is happening with the brew controller. I'm in the process of adding in code to simulate the brew day and show what is happening.