OneSignal is an app and web-based service that enables developers to create cross-platform push notifications for their apps and websites. It provides a platform for developers to send real-time notifications to users of their apps and websites. The notifications can be targeted to specific users or sent to all users, and can contain images, text, and buttons. OneSignal also provides analytics tools to track the delivery and effectiveness of notification campaigns. It also provides an easy-to-use SDK to enable developers to quickly integrate push notifications into their apps and websites.
Discontinued Probably discontinued: last updated in 2016, the app never made it out of alpha.