I wish there was a way to do local peer discovery with WebRTC. Right now both endpoints need an active Internet connection and a shared identifier (in this case a special URL) in order to find each other. Can't do offline local sharing.
If one end of the connection is a native app like this you have plenty of other options. Browser to browser is the use case I'm talking about.
It could be done with a browser-owned dialog to select peers instead of exposing all local peers to the web by default. Similar to the web MIDI API or others that expose local devices only with explicit user permission for the specific device.
I solved this issue by implementing a webtorrent tracker[1] client. Signalling server is still needed, but with this approach any webtorrent tracker can act as one.
Sharing identifier maybe we could do with qrcode, chirp audio protocol, nfc tap. Ios has peerconnectivity that works really as p2p network but sadly no web api and doesn't work android (not sure someone reverse engineered protocol)
Somebody indeed has, but since it uses a custom low-level 802.11 variant, I don't think it's feasible on (at least non-rooted) Android devices: https://github.com/seemoo-lab/opendrop
