My attic exhaust fan gets turned off for 5 minutes when my gas hot water heater turns on, to allow the flue to establish a draft.
I have an Arduino monitoring the temperatures (and a whole bunch of others, along with the status of the HVAC control lines coming form the thermostat), which then sends commands to my X10 system via the TW523 port on my XTB-IIR.
I've only played with the Arduino->X10 connection for a few weeks, but I see TONS of potential out there. There are a bunch of projects out on the web, but I haven't seen anyone put together a *real* automation controller built around one. yet.