Have you considered developing a plugin for Tasker ?
Tasker I a very well known automation app for android, which exist since a long time and has a lot of plugin available. I have heard that developing a plugin for it was fairly easy, even though I have never tried myself.
Such a plugin could bring a LOT of projet possibility
I am using Automate for android (which is way simpler than tasker) to send commands to my arduino, specifically to open my blinds when my alarm clock rings in the morning.
You just have to use the HTTP request block and fill it: