I've just built the prototype of the Repatcher-Extended, an Arduino patchbay matrix controller for Pure Data patches. It is based on the rePatcher by Open Music Labs (http://www.openmusiclabs.com/projects/repatcher/), extending it with shift registers and multiplexers. You can check a demo video here
You can get both the Arduino and Pd code here https://github.com/alexandros301/Repatcher-Extended