OneSignal - Customer engagement platform used by over 1 million developers and marketers; the fastest and most reliable way to send mobile and web push notifications, in-app messages, emails, and SMS.
Pushbullet - Pushbullet - Your devices working better together
Braze - Braze is an engagement platform that empowers growth by helping marketing teams to build customer loyalty through mobile, omni channel customer experiences.
Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
Airship - Mobile marketing solutions across all major mobile platforms.
Gotify - a simple self-hosted server for sending and receiving messages