ntfy (pronounce: notify) is a simple HTTP-based pub-sub notification service. It allows you to send notifications to your phone or desktop via scripts from any computer, entirely without signup, cost or setup. It's also open source if you want to run your own.
Really simple notifications for scripts, server status etc.
curl -d "Backup successful 😀" ntfy.sh/mytopic
If self-hosted, obviously change the
ntfy.sh to your own domain.