Hi! My name is Marcin. I am a User Interface Designer (http://www.userinterfacedesigner.pl/) and co-founder of Mir (chat client) (http://mirchat.pl/). Your offer caught my attention because it fits perfectly in know-how that I have as well as complete source code which I own (with self-made communication protocol). I think that my experiences can help to create a communicator that perfectly meets your requirements. I have worked on every stage of developing Mir Chat from start to finish (http://www.mzajac.webd.pl/samples/) . It has been made using the Qt framework (which supports mobile platforms like BlackBerry, iOS and Android although from what I know Windows Phone is still in a pre-alpha state)
The target of my program is obviously entirely different, however I believe that with appropriate layout he can suit every needs.

If you are interested feel free to contact me

Marcin Zajac
martin@userinterfacedesigner.pl
skype: t15szary