This app can help you remotely (over cellular or WiFi) control your home or business sprinkler system, with convenient aspects such as:
-A visual live monitor of which stations are running.
-Automatic zoning
-Automatic cycles
-Semi-automatic starting
-Manual timings
-Temporary weather delays for rain.
To install this requires around $40 and a couple hours.

Installation instructions are available at https://datadeer.net/rs

The app has instructions for guiding you through the entire process including: Buying the parts, setting up the Raspberry Pi, setting up the relay, and using the app's interface.

Raspberry Pi is a trademark of the Raspberry Pi Foundation