Simple Iphone App with existing Joomla Server - repost

Freelance iOS developer required to quickly build a app using an existing Joomla site. Hopefully you have already built a similar app. We are looking for function, basic layout, and source code. The basic function is Login in/Registration, and the finding, downloading, creating and editing of articles. These articles are all grouped in to catalogs (we are using K2 categories). Please note, that we want to be able to download all the articles from a selected Catalog into the app for latter access off line. You can use existing plug-ins, or build Joomla plug-in(s) to expose the site via REST. Part 1: The app will search for catalogs or articles, then be able to select a catalog and download to the app the articles of that catalog. This will not be a Web app, but will use iOS to find, download and create content in an existing Joomla server (MySQL and PHP). Part Two: the app will be able to register and authenticate a user . The user can create /edit/delete their own catalogs, and articles with the app. Ideally we are tying into Joomla platform with existing code, with existing plug-ins, or building Joomla plug-in(s) to expose the site via REST. We are looking for a quick turn around, and hopefully existing solutions/code.