WebRTC (Web Real-Time Communication) is an API definition being drafted by the World Wide Web Consortium (W3C) and jointly in the IETF with a working group chartered in May 2011.
This is the world's first open source HTML5 SIP client entirely written in javascript for integration in social networks (FaceBook, Twitter, Google+), online games, e-commerce websites...
The client can be used to connect to any SIP or IMS network from your preferred browser to make and receive audio/video calls and instant messages.