VOIP client with XMPP chat support for Windows and iPhone/Mac platform

We are small startup soluion provider and looking for developer to help in developing SIP client, most preferably using some open source SIP stack like reSIProcate, pjsip library. It would be great if you have already developed dialer app for iPhone where you can detect Wifi vs 3G and handle through SIP server and in non-WiFi mode connect through carrier. On iPhone, a typical example is "Line2" Application. Here are basic features that are needed: - Basic call control features like Answer, Hold , Pause etc.. - Standard VOIP feature like multiline lines capability. - Automatically provision the settings - Records call to disk - Shows personal call/history - Supports G.711, GSM and Speex codec - Easy to reply and manage - On iOS platform, detect Wifi vs 3G vs Carrier connections and use path accordingly. - XMPP support to have IM messages, not SIMPLE protocol. Please respond if you are a developer and have developed such clients in past.