Naaztel

Naaztel has come up with "Mobile VoIP Client for Android" for android based Mobile phones. Android VOIP Mobile dialer lets the callers make VoIP calls through their standard Mobile phones. The biggest advantage that this Android voip provides is the huge base of potential customers who can now make calls using their standard mobile phones. The mobile phones need to be connected to the internet either through GPRS/EDGE/Wi-Fi/3G.
You do not need to have free minutes bundles to make national and international phone calls using Mobile Diallers. Just download the software and make international calls straight from your mobile.

Features :
SIP protocol support
Making and receiving calls
Codecs supported:g729, g711,GSM,G722
Phone Book (Synchronize with Phone Address Book)
Call Log
Call Status Indicator
Save / Edit Username & Password
Work with all standard SIP SoftSwitches
Android 1.5, 1.6, 2.X, 3.X, 4.X
Silence Suppression
Echo Cancellation
Registration Timeout