Anroid and iphone application for a buy and sell website

The application consist of three major functions- View an ad Place an Ad and Search an Ad. An Ad belongs to a Main category and a Sub Category. Some of the main categories should be displayed in the home page. Each functionality is explained in brief below: View an Ad ----------------- When the user click on the ad it displays all the details of the ad including Description, Photo and/or video Contact information The user should be able to call and email the seller directly from his phone. Place an Ad ----------------- A user can post his ad in this section. An Ad consist of a Category and Subcategory selection Brief description Detailed description Seller contact information Photos of the item (activate mobile camera for inserting the photo) Video link from youtube, of the item Local area of seller State of seller District of seller Price of the item Login Id and password of the user (If existing user) Login name, password, name, contact number (If new user) Search an Ad ----------------- A user can search for a particular ad. The filters included are Main category and sub category State District Keywords Mix Price and Max price The ad which satisfies the search criteria should be listed down. Apart from this we would also like to Integrate Google map to each item location. Community link such as facebook, orkut, twitter etc Use of a common platform for both the application like HTML 5.