Using WiFi/3G connection on your iPhone or iPod Touch 2nd Gen, iSip (formerly SipPhone on iPhone) turns your iPhone or iTouch into a pocket VOIP phone, so you can make cheap or even free phone calls (local or long distance) over the internet at anytime, and from almost anywhere.
Support SIP protocol
Support speaker phone
Voice mail notification
Multiple ringtone selection
Support DTMF tone (RFC2833/Inband) during the call
Support G711 and GSM codec
Support using alternative RTP port
Support Stun for NAT Traversing
Support Sip Proxy
Capability of mute/hold call
Support multiple SIP accounts
Dial directly from iPhone's address book
Support prefix dialing when make call from address book
Redial from recent call list
Shortcut to make regular celluar call
And much more ...
Support and Questions:
SipPhone on iPhone used in enterprise
Here are a couple YouTube videos made by our customers demonstrateing this usage:
Here are a few of our first App Store customers have to say about SipPhone on iPhone:
This is the best voip app ever! -- by SonnyKovacs
Better than fring for SIP voip -- by cubalibr...
Awsome -- by MikesT...
Just what I always needed! ... a must get application -- by malta25
Excellent App -- by Andrew She...