The OmniPro II actually serves as the sprinkler controller. I purchased 2 Form C relay contacts (HAI part # 19A00-1) so that I may convert up to 16 12-volt switch outputs to 16 24-volt outputs (required by sprinkler valves). All valve wiring (in addition to my security/automation wiring) runs directly to the OmniPro II controller which, in my case, is installed in a closet inside my home. I have multiple consoles installed in strategic locations (doors to outside, living room, etc.) so I can turn on/off lights, arm/disarm the security, run sequences, and start/stop sprinkler zones/areas if I want to bypass the auto-sequencing. Each console is connected to the controller. To program the controller, you can use the consoles for basic setup, but I use HAI's PC Access software to setup all programming on my PC and then upload the information to the controller. The interface is extremely intuitive and no programming background is required.
As far as programming sprinkler zones is concerned: each zone is is completely programmable as to "when", "how long", "delay between zones". Of course you can start/stop multiple zones simultaneously if desired (and your water source supports it). The real nice thing is I program zones to water for a specified time starting X minutes before sunrise.
In my case, I group multiple sprinkler zones into "areas" ("scenes" to the OnmiPro). When I tell an area to start watering, the first zone in the area runs for a specified time and then the 2nd zone runs for a specified time, and so on. Once all zones in the area have been watered, I typically set a loop counter so the entire area will automatically run through its sequence again. My soil is very compacted so I have some control over the runoff
If desired, the OnmiPro can be setup to run sprinkler zones/areas by dialing into the controller from outsied the home, or even slicker, accessing the controller from the internet. Additionally, you can use your internal phone to run sequences (i.e. remote control). In fact, I use our cordless phone out in the yard to turn on/off sprinkler zones when adjusting sprinkler heads or replacing nozzles.
Last winter I was too lazy to rent an air compressor to blow out my system so I hired a local sprinkler guy to come perform the task. I pulled out a lawn chair and sat next to the guy with my wireless laptop and a beer...turning on and off zones during the blowout.
Pretty damn slick!