Message/Queue service provides a way to post a message on queue and then receive that message on other end. If you are planning to have private chat between your users, this will not be a wise solution to implement because you will end up using multiple queue inside your application. Since we have restriction in creating queue (50 per app) this might be bottle neck for your app. Also, this is an offline messaging and not suited for real time chat application.
We already have AppWarp solution which is well suited for this kind of application and can be implemented on Android/WP and PHP(using JS SDK) to implement the chat feature. Here are the few links that might be useful in your case to look for
AppWarp Chat Walk through
Android Chat Tutorail Using AppWarp
Let me know if it helps.
Thanks
Ajay