I have 6 zones and would like to add more. Adding trees, a raised flower/vegetable garden are just a couple examples of what I'd like to do. I have a water source close to all appropriate areas and adding a solenoid valve is not too hard, but running new wires is not trivial. It would be nice to either have the option to control solenoids via RF with a local battery to activate the solenoid (I've read of some that use a 9V battery) or a device (set of two actually) that enable controlling 2 or more zones using a single pair of wires (this would require the additional solenoid valves to be close to the one we are piggy backing off of).

For this latter issue, I found a video of a device that seem to do just this, but a native solution might be better... especially if we can eliminate the device at the controller and just add a device at the solenoid valve end.

https://www.youtube.com/watch?v=WHCneUBuko8

See 1:21 for a diagram of what I was thinking... which happens to already exist.