This tool is free, open source, works on Windows, Linux, and MAcOS, with a shell and web based interface. It allows one to easily send notifications to phones. One can use it simply from the shell with an app on the phone, or create your own server on your home machine optionally with docker.
I find it useful, one can hear all about on the video.
My usage is simple: I have the ntfy app on my phone, and I send messages to it using curl .
It is handy for things that will take some time: system update; rebuilding a compiler.