You know you can get a plug to go in the bottom of a droid that gives you serial, etc? You can then plug an AVR or whatever into your droid and use that to do hardware interfacing, i.e. switching the enlarger directly from the phone. In fact, I'd be surprised if you couldn't use the CTS line or something on an FTDI chip to toggle your relay, no extra logic/micro required.
How do you deal with the screen fogging your paper?
PS your link seems broken ("We're sorry, the requested URL was not found on this server.")
PPS devil's advocacy.