I think it would be easier than you think. Take a look at sprinkler systems for yards, which operate on a timer, controling various zones. Something like that, but add in an alarm system that uses a smoke detector to trigger the alarm. Put the smoke detector in a couple places around the house, outdoors and another on the, no make that two on the battery station. Also don't forget your shop, that will need four smoke detectors. To set it off from the house, mount a keypad inside the house and the 911 feature that most of them have should be able to trigger the sprinkler, rather than calling the police. You may or may not want to hook your house alarm up to this same system, not sure. You might need to install some transformers to change the voltage to what each part of the system uses.
I don't think you would need to have that much water spraying on the house, as this would be a preventative, not a fire-fighter system. As long as you got it on before the place got hot, no embers are going to catch it on fire due to a spray keeping the ignition temp low and putting out small air-borne embers.
You could do the "fire-fighting" type system, but I prefer not to have it start at all, instead of trying to put it out once it starts.
David from jax