A VoIP softphone is required for Mobile Cell Phones (symbian, windows mobile)
To get a clear idea, plz check :
fring,Yeigo, Nimbuzz.. etc..
Basic features :
1. Fully featured IAX client
2. Instant Messaging with known services (Yahoo, google, msn)
3. Prefered codecs (g723, g729 and speex)
4. Should be user friendly and flexible to learn and use.
5. Support for registration, download and installation directly from the site to the mobile through SMS
* Candidate should have references in similar projects
* Source code should be provided.