ejabberd module development for mobile client

Dear Friends,

My requirement is as follows :
a user from his mobile application is going to send his Geo location to the ejabberd server and the server needs to store his location and return a list of all users that are close to that location (say with in 5 miles). Question is :
1)how should I develop this module?
2)how should I configure this inside ejabberd 2.1.11(on windows 7)?
3)how a client (writen in objective c) is going to call this module and set / get the Geo location information?

I am really new to XMPP, ejabberd and mobile application development so your help would be really appreciated.