Jami on desktop, not on phones yet:

https://jami.net/eleutheria

Available only for desktop users for now, the new Push-to-talk feature offers a new effortless way to communicate: simply press a button for hands-free, instant, and convenient audio messaging. It’s like in the olden days of gaming when gamers would key bind the Push to talk feature to be able to talk when necessary.

So jami all the way, 🙂