Mobile cellphone SIP Voip Application for Android

Req. Summary: We are in need of a seasoned Mobile applications technician / programmer: We need a very simple application, with our logo on it, for SIP Voip Calls from Android. We have a SIP server, we need this application to connect to our server (user will just see the fields username, password). User doesnt need to write the server ip address or port or protocol, just username and password. Then, he can see his actual balance, and dial to make any call with its mobile device. Application MUST use the G729 code. This is a mandatory requirement. Look forward to your bids.