If what you are asking is the ability to control a sprinkler valve wirelessly, I have already posted on that subject below
There is no cheap solution in the US so far that I could find, but I did find the necessary components from a company in china. I am in the process of assembling it together and will post back in my thread above if successful.
It includes a transmitter that takes the Valve output of the Rachio as input and transmits the on off to a Receiver that opens / closes a DC latching sprinkler valve). The receiver has ports for a Lithium battery and a solar panel and has a charge controller on board so it can keep the battery charged using the solar panel during the day. I bough a 12V 3ah LFP battery in the US, and a 6W solar panel to do the charging.
But if a lot cheaper than the US solution I mentioned in my thread, this is still almost $300 between the receiver, transmitter, battery and solar panel.