Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
restdb.io - restdb.io lets you create databases and REST APIs quickly. Development databases are free. Powerful web-based and mobile-friendly data management.
Parse - Build applications faster with object and file storage, user authentication, push notifications, dashboard and more out of the box.
Kumulos - Made for the business of mobile app development, Kumulos helps you manage the commercial and technical performance of Apps, so you drive a better outcome for your clients.
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA
AWS Amplify - JavaScript library for app development using cloud services