I use a deep well pump to supply the sprinkler system with water. Once the well water level runs low a swimmer switch cuts the pump power until it is refilled. My Rachio 3 does not know that watering stopped and happily continues to switch zones.
The next gen of Rachio control should offer programmable inputs/outputs.
If I had an input to tell Rachio that the well is empty and switch this back once the well refilled itself, I could water forever. Rachio could stop at the right time and start by itself.
I wonder if the unused rain/freeze sensor inputs would help, but I doubt it, since a toggle every 15 min would not make sense to the control. Immediately after a rain or freeze switch impulse it might not water until the next schedule starts.