I would like to control multiple sites from one app. This would also be great for commercial sites, especially if the controllers could handshake with each other or act as repeaters.
Also, I would like to suggest an add on module that could register water flow via a special replacement master valve or an add on to go in line before irrigation valves. This would be a simple pulse signal that could be hard wired or transmit digitally over the master valve 24v trigger wire (as a carrier), or transmitter. The controller would learn the pulse compared to know flow needs of each separate zone. If that flow rate substantially increased, the controller could shut off that zone and notify the owner of excess water -- broken zone. The controller could also take the pulse signal and use it to keep a log of "units" of consumption for the total system -- giving very accurate intel on changes to system that increase water conservation.
It would be great to have 30-40 zone units, with these features, for commercial applications. I would replace all 20 on one property in a second. A simple wi-fi net would be great.