wirte simple viber extension module for opencart

We need a simple extension to be used in opencart. the extension should be compatible with opencart 1.5 and above. It should be easz to install without over writing any existing documents. It should have a backend interface to add the Viber ID and define the position of the module. It should be possible to let the module float at the edge in the frontend. It should allow the visitors of the site to call a predefined number (in the backend) by launching viber. It should look similar to the existing skype extension shown here: [login to view URL] the extension should include all images needed. the freelnacer will deliver a zip file including all files needed to be uploaded to the root folder of opencart. The extension should be then instalable via the opencart backend in the modules menu.