I thought I would share my recent addition to my system. I have a Kohler DTV+ shower that has a network interface as well as a web portal for minor changes and has some control over the device.
I decided to peek around and inspect some of the web elements to discover a repeatable URL that I can use to trigger shower start and stop. You can discover these by simply using 'Inspect' in chrome for example and log the devices activty as you activate/deactivate the shower for example.
Below are the two commands I am currently using in my system, you can modify the valve outputs and temperature. Mine right now is set only to turn on valve 1 at 38C. Right now I use these links as an image in announcements (to trigger the weblink as an image on my T3), I then have it linked to custom buttons on my bathroom screen as well as IFTTT/google assistant (OK Google, turn on the shower) . I do not have the Chowmain driver to push weblinks but I think I will update to use that to trigger the URL in the future.
It is not flawless, and I would caution when trying to discover the correct links if you enter one incorrectly the Kohler web portal will become non-responsive and you need to power cycle it (this took many power cycles for me to figure out correctly).
Nonetheless, I can now tell my shower to turn on an off which I was quite excited about.