emitter.io - Real-time communication service for connecting online devices.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
Socket.io - Realtime application framework (Node.JS server)
Supabase - An open source Firebase alternative
Pusher - Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality via WebSockets to web and mobile apps.
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA