SMS Multiplier with SMS Gateway

i would like to get a program+basic website which will do the following, kind of multiply SMS delivery (back and forth) the system should work like this 1)a user sends an SMS to a short code with certain format (lets say i have a group called FAMILY) shortcode+FAMILY or F only+message a user can have more than 1 group in their account 3)these groups should be created in a website where the user previously has been registered and he created the group FAMILY (so the information of his cell number and the group name is entered) 4)other people can registered to this group entering their cell phone number in the website. 5)once any member of a group, sends an SMS with the format shortcode+FAMILY or F only+message the people member will receive the message (so 1 sms will reach multiple users), any recipient will have only to reply to reach the whole group 6)user registered will be able to select whether they want to see the message in their handset (default) of if they check on the web, they will be able to check it in a passive chat-room(this is room where all messages posted are seen, but one can not write form there) at least in order to reply they should send an MO SMS 7)We will charge SMS by MO and MT, so the the service (your program)will have to talk to 2 connections (1 connection is for receiving MT and the other for sending) 8)all sms messages will go through sms studio ([login to view URL]) as the gateway, this interfaces very easily with any external application (ODBC or NAMED PIPE)it can be downloaded for free 9)some recommendations are welcome (this is some kind of basic twitter) Budget is US$400