* http://quickblox.com/ - A communication backend for instant messaging, video and voice calling, and push notifications
* https://pushbots.com - Push notification service. Free for up to 1,500,000 push/month.
* http://www.dreamfactory.com/ - DreamFactory is an open source backend platform that provides all of the RESTful services you need to build fantastic mobile and web applications
* https://www.mashape.com/ - API Marketplace And Powerful Tools For Private And Public APIs. With the free tier, some features are limited such as monitoring, alerting and support.