Installation of the device is easy.

Here is the before photo of a standard Sprinkler controller wired to 4 zones / valves. The white wire is the "COM" wire, common to all zones.

Here we interrupt the COM line with a relay connected to a Particle Photon, creating a WiFi enabled control system.

Installation is easy.
The project box shown is a sample box - the final device, which would be built with a custom PCB, would be much smaller.