Messaging application (Mobile Website)

Messaging Application The communication application will be used as a module in a web based (for now) user environment. Attached you find a screen shot. The application is used for communicating with and between different users. Admin to users, user to user, user to multiple users (group) and push messaging. A pdf with everything explained is attached. Please reply by explaining a little bid of the solution you propose and only reply with relevant references, not just general websites.