With OpenSprinkler you can easily switch devices that have an HTTP interface and can be reached via WLAN.
Provided, of course, that the device can be controlled directly via HTTP commands. Pure “cloud” sockets do not work or would have to be changed with a firmware update. See the TASMOTA project (https://tasmota.github.io/docs/)
However, this is not necessary for the Shelly sockets (e.g. Shelly Plug S), as they already have a web service and can therefore be switched on and off.
1. Connect the Shelly Plug to your WLAN as described in the Shelly instructions
2. If the device is now successfully connected to the WLAN, you will need its IP address. In the Shelly APP, select the device and open the “Device information”. Here the IP address is behind “DEVICE IP”.
3. Open the OpenSprinkler APP. Select a free zone (using the gear on the right), click “Advanced” and then select “Station Type”: “HTTP”:

Instead of “192.168.0.78” enter the IP address of your Shelly socket, which you read out as “DEVICE IP” in point 2.
Very important: The “On Command” and “Off Command” must be entered EXACTLY as shown, i.e. everything in lower case! Note in the middle is the number zero.
For copy/paste:
relay/0?turn=on
relay/0?turn=off
On the “Basic” page you still have to deactivate “Disable” and “Sequential”.
Now you can use this zone like any other. If you connect a pump here, you can also configure it as the main irrigation zone, which is then automatically activated before each irrigation.