//afone is the reference implementation for SIP Telephony on iOS that can be used on different SIP stacks with no effort. This is a ready to use softphone with the following features:
* video calling
* mute/unmute
* hold/unhold
* DTMF tone sending
You will need your own SIP server to connect to or a CPaaS provider account and credentials.
Its Open Source and available on GitHub under https://github.com/automat-berlin/afone