1. Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.

  2. PubNub is a real-time messaging system for web and mobile apps that can handle API for all platforms and push messages to any device anywhere in the world in a fraction of a second without having to worry about proxies, firewalls or mobile drop-offs.

  3. API development tool for Web and Mobile developers.

  4. Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality via WebSockets to web and mobile apps.

  5. restdb.io lets you create databases and REST APIs quickly. Development databases are free. Powerful web-based and mobile-friendly data management.

  6. One Complete Database Service that does data-storage, search,real-time and a whole lot more.

  7. OneSignal is a free push notification service designed for mobile apps and games.