These systems are very expensive. Hunter and Rain Bird make one. They can be controlled via your computer.

Here is a link that might be useful: do_it_your_self_site

If you are setting up a complete home automation system then you don't need any proprietary irrigation system. Just get whatever 12v computer controlled relays that your system supports. Hook those up to the solenoid on the irrigation valve. Let the home automation system take care of everything.

Here is a network sprinkler controller that you might be able to use: (search: EtherRain). It has an Ethernet port on it so you can connect it to your home network (either directly or if WiFi you'll need a wifi access point). They provide scheduling software for XP/Vista, and click the link below for Internet scheduling that lets you set your irrigation schedule using your browser and it will control your irrigation from the net. Compared to smart controllers it's fairly inexpensive, and if you are interested in saving water it will most likely end up being cheaper than the lower cost hardware store controllers.

cheers,

Here is a link that might be useful: Smart Irrigation Scheduling