@Trommeltotti
I know that the current 2.8 boards have an 8 pin extension. You could very easily hook that up to a Cat5 jack and run a normal ethernet cable between the boxes. You would have to make an extension board and put it in the second box. Best part of this is that Cat5 jacks require no soldering.
@Synthex
Thanks for the great work on both your AIO and inputs boards. If I wanted to add another 24 inputs to my 2.8 board, could I just remove my Atmega32 and replace it with an Atmega644, then make the expansion board? Is there anything else I would have to do? Besides programming of course.