HD Dialer Pro offers a simple user interface and superb audio quality for smooth Voice over IP experience. Key features include:- Bluetooth support.- Lowest battery usage with highest reliability / stability on all iPhone models.- Lowest audio latency of all iPhone models.- Excellent audio quality, even on older devices.- Supports calling over WIFI/EDGE/3G/LTE.- SIP stack fully compliant to RFC.- Background / multitasking support.- Speakerphone mute and hold.- Supports sending of DTMF.- DNS SRV.- Built-in echo cancellation.- STUN support.

HD Dialer Pro alternatives

Talkonaut

Talkonaut is a free Jabber (XMPP) client for your iPhone or iPod with free peer-to-peer voice calling over Jingle Audio extension compatible with GoogleTalk. Talkonaut can be used with any standard Jabber account like Gmail, Gizmo5, Jabber.ru or from your corporate Jabber server. Push notification is not currently supported.