iPhone Sip client released today via Fring
I just installed it myself. Works great, and it's free.
Process of Installing
http://www.fring.com/iphone/
This application is meant for jailbroken iphones only.
Update, after you dial out, the dial pad disappears, for good. So no IVR's or voice mail checking until they come out with a new version.
The call quality will be very poor using the EDGE network, just like if you tried to do VOIP over DialUp.
My roommate has a TILT with Windows Mobile 6 and the AT&T 3G Network here in Phoenix is fast enough to support near flawless communication to my home Trixbox using Fring as the client. Only complaint is that it takes about 2 seconds once the call is connected for the audio stream to get brought up. Also, if you leave the phone registered with Fring running, your battery will last less than half of normal.

Member Since:
2007-10-17