This weekend the New York Times reported on the Cyber-Rain XCI. The system networks to your home computer to access the latest weather reports for your area before turning on the hose. The $350 kit includes a wireless controller that connects to your existing sprinkler system. A wireless access point connects to your computer. The two nodes talk to each other in order to make the most out of the upcoming weather.
The controller also lets you configure up to eight zones, so if you succulents in one area of the yard and tropicals in the other you won't be dousing or droughting either.
I see some very funny WarHacking moves here though ;)
Wireless control of your sprinkler system