You wouldn't need a module or app for this; you would add the integration into FreiChat.  I am not up on how UNA handles sessions but I am going to guess that it is along the lines of a session cookie that holds the member info that is logged in.  Say there is the member ID or whatever UNA uses; you use that ID to query the database to get the member's name and avatar to pass along to FreiChat; It then sees the member logged into UNA and logs them into FreiChat to start chatting with other members.