Socket.io - Realtime application framework (Node.JS server)
Pushbullet for Mac - Send your iOS notifications to your Mac
Ably - Serious realtime infrastructure
Pusher Beams - Send push notifications programmatically at scale
Pusher - Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality via WebSockets to web and mobile apps.
Muzzle - Silence embarrassing notifications while screensharing