Parse - Build applications faster with object and file storage, user authentication, push notifications, dashboard and more out of the box.
EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
AnyPresence - AnyPresence is an Enterprise Backend as a Service for mobile app development and API augmentation.
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.