Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Notix.co - NOTIX is an audience re-engagement service based on web and in-app push notifications that work for both desktop and mobile devices.

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

Airship - Mobile marketing solutions across all major mobile platforms.

Strikethru - Strikethru is a kind of to-do list notebook for managing work lists and staying updated with the important tasks.

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.