I use jit.si as replacement for Skype. It's in browser, encrypted, p2p and EFF approved.
I don't know if they have apps, but as far as I know their server code is on github.
I don't know if they have apps, but as far as I know their server code is on github.
I personally use jitsi because it is FLOSS software and it's less likely to send conversation contents to the NSA or other dragnet surveillance entities. But it's not end to end encrypted.