Pushbullet - Pushbullet - Your devices working better together
Gotify - a simple self-hosted server for sending and receiving messages
Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
Amazon SNS - Fully managed pub/sub messaging for microservices, distributed systems, and serverless applications
AirMore - AirMore is a cross-platform toolset that can help you manage any Android device wirelessly.
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.