Node.js WebRTC client
I came along the same problem and stumbled upon these two gems:
https://github.com/helloIAmPau/node-rtcSadly it is lacking any documentation.
Howeverhttps://github.com/js-platform/node-webrtcseems more reliable to me.
You should check out licode. Their open source webrtc multi-point video conferencing bridge that runs on top of node.js. Their server acts as a webrtc client, which then bridges audio/video to other webrtc clients. You might be able to reuse some of their c++ code that uses libnice(for ICE protocol) and libsrtp(for SRTP stack), and then wrap it inside of your own node.js module to create a successful webrtc client.
Obviously most of their code you don't need, but I think their server gives a good example of a working SDP that you need to send back to the browser in order to establish a successful webrtc connection.