Very nice VoIP Mobile Dialer for iPhone/iPad.
iOS versions:
VoIP SIP SDK for iOS 8;
VoIP SIP SDK for iOS 7;
VoIP SIP SDK for iOS 6;
SIP :
SIP servers support (including Asterisk, PortaSwitch, VoIPSwitch, etc.)
Voice and Video calls
Status messages
Codecs available :
G.729
H.263
H.263+
H.264
G.711-ALaw
G.711-muLaw
OPUS
Speex
Theora
GSM