Edyn has a trigger for moisture level above or below a certain threshold and it can trigger an rachio event. I've set up a applet to water a zone if the moisture level falls below a certain amount.
This is one approach, but I'd rather not bypass all the secret sauce edyn has done with the flex schedule. I'd rather rachio provide an interface to update the moisture level for a particular zone. I'd be interested in seeing the differences between what edyn is reporting and what rachio has estimated.