While this provides a lot more functionality than just the bare minimum it says on the label, I’ve had great results with something like build-something-here && notify-send "check your build". Sure, it’s pretty simplistic compared to the automatic shell integration and the other advanced features ntfy provides, but it serves the majority of usecases (for me at least).
build-something-here && notify-send "check your build"
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Are you aware of wall and mesg unix commands? They might serve your purpose, I’m not sure.