Android Sip Phone

We have a Asterisk PBX and we want to build a simple phone application that would accept/allow incoming and outgoing phone calls using the Asterisk PBX (behind the scenes) along with ability to make few changes to user preferences and settings. Currently we are using something like sipDroid. We would like to integrate this application with our existing application so that user doesn't have to leave our application in order to initiate phone calls. Quality of the voice is very important and we need high quality (business quality phone) phone conversations (as long as we have high quality voice and we can extend it for video conversations, etc). I know few SIP stacks that can be helpful: [login to view URL] [login to view URL] We would like you to use efficient coding with appropriate comments and documentation. Please do not use any libraries that you have disclosed prior to starting the project. If you have the required experience and you have time to handle the task, please send me the summary of your experience (with phone/pbx), your bid, time frame, libraries you would use, and time frame to complete the task. Thank you for your time.