Pusher Beams - Send push notifications programmatically at scale

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.

Truepush - Unleash limitless possibilities with Truepush and save up to $600 monthly. Free up to 10K Subscribers on all features.

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

PushOwl - Re-engage website visitors with push notifications

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