I have some repos that use WebRTC to connect clients, I created this experiment where I will try to send the needed ice data via audio, to connect peers:
https://github.com/AquiGorka/webrtc-connect-experiments
On the games side, I am coding a web version of Kuhhandel (a german boardgame) where people play using their smartphones: https://github.com/AquiGorka/kuhhandel
Here I used webrtc data channels to send a smartphone's gyroscope data to a webapp that renders a virtual puppet. The puppets control bar mimics the smartphone's orientation: https://github.com/AquiGorka/puppets
For really simple connections you can use this: https://github.com/feross/simple-peer