Oh, this is interesting. I have been messing around with a WebExtension for dumping encoded WebRTC media streams by intercepting streams on RTCPeerConnection.addTrack, but it doesn't work reliably since the current WebRTC encoded stream API(s) only supports a single reader, so if the actual website is also using the API, it either breaks the site or it's impossible to intercept the media. This seems like a nice workaround, I had briefly considered some kind of proxy but I wrote it off since WebRTC traffic is encrypted, I never considered proxying the peer connection API calls themselves. Pretty clever.