Multi-user (many-to-many) audio-calling using mesh networking model.
You can write cordova/ionic/phonegap based iOS or Android apps for this demo as well. You can download an open-sourced cordova app both for iOS and Android as well.
You can run same demo on Safari-11 as well. (both on MacOSX & iOS)
You can install following Android app and join meetings from this demo: https://play.google.com/store/apps/details?id=rmc3.audioconference
Microsoft Edge is also supported.