Pusher Beams - Send push notifications programmatically at scale

Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop

Notisave - Notisave – Status and Notifications Saver is an exceptional tool created and published by Tenqube Inc.

Pushbullet - Pushbullet - Your devices working better together

Notin - Notin – notes in notification app helps users in creating alarms to get reminders about important tasks right on the home screen.

Gotify - a simple self-hosted server for sending and receiving messages