We just released a new version 1.1 Beta of the Deft response block that has support for audio conferencing. This plugin is designed to deeply integrate conferencing functions into Moodle. In this case a teacher can make a button appear in block in a course or activity that allows learners to talk to each other while they are engaged in the course activities with one click of the button.
A demo is available at https://deftly.us. Following Audio conferencing link and log in with the test accounts on separate devices.