VPN embedded sip dailer

we need a VPN embedded sip softphone before registering to the sip soft switch the soft phone must have the capability to establish a vpn between the softphone and softswitch . 1. Fully featured SIP client. 2. Must work with any kind of Soft switch which support SIP. 3. Must support multiple codecs (G711 ,G726 ,G729 ) for sending audio stream. 4. Must support DTMF dialing during a call. 5. Can run behind NAT or on private IP. 6. Can display balance on successful login 7. Can run on application layer so it supports GPRS/EDGE/WiFi/3G for internet connectivity. 8. client can hear remaining balance by listening to IVR. 9. The ability to change voip provider IP and logo in the software if needed. 10. This software will run on the phone having Symbian or Windows Mobile 5 and 6. Experience in developed similar product with a demo or sample reference preferred. All source code and documentation must include.