IPhone application - Simple message app that alerts others in same group..

Hi,

I'm after a simple message app that lets friends in the same group send a group message. The friends that then receive that message can respond with accept or decline. The app will have notifications to alert user of new message and notifications for accept or decline message....

I believe it's a pretty simple app. I can design the user interface and how it will flow together, but i'd like a quick quote from a dev. I prefer to work with one man operations. Thanks.