I programmed a very simple Software in Arduino with a Telegram Bot.
Each user in our appartment can switch on the warmwater whenever he/she needs warm water. This may be needed for showering, washing dishes,....
This Switching on is done with your personal mobile and the Chat App Telegram Chat App
You may have a look how this Chat app looks here.
The User can select with short cut buttons how long the waterpump is running and when it is switched off automatically.
You May find the complete SW here: