ntfy is an Android client that allows you to send push notifications to your phone from any Bash or PowerShell script, or from your app using PUT/POST requests. This app is a free and open-source HTTP-based pub-sub service that enables you to subscribe to topics and then publish messages through a simple HTTP API. With ntfy, you can stay informed about long-running processes, failed backups, and server logins.

This app is perfect for those who want to keep track of their processes and receive notifications when they're completed. You can subscribe to any topic and then publish messages through a simple HTTP API. The app is easy to use, and its interface is user-friendly. Also, you can find more examples and usage instructions on their website.