There are some services out there that will help with just this sort of thing too. The one we're looking (Frontline) at tries to be a bit more intelligent too, and will prime itself once it knows fires are close (We're checking to see if it is fail safe, where it primes itself once it stops hearing an 'all ok' message, rather than waiting for a 'danger' message, which may never arrive if cell coverage or our network connection fails). Frontline only seems to want to work with their own installations, not custom installs. We're looking to find ones that will also use local heat sensors, to start firing water and fire foam onto the roof and eves and around the properly only when the fire is right there, saving water until it's needed.
Some will even tap into a pool as well. Our pool guy was concerned about that, saying we should make sure it knows to turn the circulation pump off so it wont burn out.., but we pointed out that if we lose a $1200 pump but save the house and all our stuff, we'll gladly take that....