webrtc without a browser

If you want a Python implementation of WebRTC, give aiortc a try. It features support for audio, video and data channels and builds upon Python's asyncio framework.

The server example illustrates both how to perform image processing on a video stream and how to send video back to the remote party. Aside from signaling there is no actual "server" or "client" role in WebRTC so you can also run aiortc on your raspberry pi and have it send video frames to whatever WebRTC endpoint you want.

You can use the native library and connect it to the face recognition server. You can use either the google implementation of webrtc or a more recent implementation (by Ericsson) called openWebrtc. The developers of openWebRTC are very proud of running their implementation on various pieces of hardware like raspberry pi and iOS devices.

If you don't what to mess with a native library you can use a nodejs binding for webrtc (for example node-webrtc or easyrtc)