Pusher Beams - Send push notifications programmatically at scale
Mentioned By - Learn when your site is mentioned by other sites for free
OneSignal Push Notifications for Shopify - Abandoned cart, automated campaigns, robust analytics.
Ethereum Push Notification Service - Protocol for incentivized, blockchain based notifications.
Push Notification Preview - A simple tool for previewing push notification copy
Now Push Notify - iOS does not support browser notifications today, but Now Push Notify makes this possible.