I am also interested in the use of OpenSprinkler as a “Smart” or ET (evapotranspiration) aware controller.
mathferret: please keep us posted on any progress you have made in this area.

One very simple feature would to be the ability to adjust one or more zones’ watering times by a percentage through a
HTTP GET. This would allow the ET adjustment to be computed on a separate host, which may have information supplied through an internet or local weather station, soil moisture sensors, etc, then applied on a daily or just-in-time basis.

It would also be interesting to have ‘cycle-and-soak’ programs on OpenSprinkler. This is useful when watering on a slope. So you can cycle on for 10 minutes, off 10 minutes to let the irrigation soak, then cycle on again, and so on until you have applied the full amount of irrigation to the zone. I imagine this might be possible already by setting up several programs on the controller?