The arduino is really starting to become prevalent for hardware hacking. [Nash] used one to take control of his Gaggia espresso machine. (They’re really decent little machines) He popped in a LCD display, some solid state relays to control the pump and the heating element, and an AD595 to interface a K type thermocouple. It looks like an excellent hack, but for the love of god man – get a better grinder!
He describes the original mod here, and added a small gallery of internal shots here. From the latest comments, it looks like the guys are RepRap project are even interested in the thermocouple PID control that [Nash] implemented.