I made such a thing ten years ago with an ESP8226 and a basic iOS app built using HTML and javascript. It still works perfectly. The valves were 12v solenoids

I made such a thing ten years ago with an ESP8226 and a basic iOS app built using HTML and javascript. It still works perfectly. The valves were 12v solenoids from ali express, and the plumbing was from the hardware store. I almost guarantee it was far, far cheaper than this project.