Next to lacking XMPP, SIP seems to be a missing core function.
I trust Jolla is working on it to gain my continuous support and to lift Sailfish as the best mobile telecom OS

Meanwhile does anybody care to test if SIP for "there-must-be-an-app -for-that-Android" works?

The csipsimple program is pretty clean and no Playstore needed.

https://code.google.com/p/csipsimple/

My thanks