Desenvolver um aplicativo para o iPhone

My company uses a PHP opensource project management to keep track of our projects. We'd like to have an iOS (maybe Android too) app that could be used offline and sync with the web interface that is hosted in our webserver. The program is the todoyu and the sourcecode can be find in www.todoyu.com. We don't need all the funcionalities. Only the projects section and part of the portal (actualy we don't need the portal, only some filters). So, the app must read the projects and tasks, be able to change texts, dates, responsible, status, etc. and sync the changes. I'd like to know how does it costs and how long it takes to finish the app. I'd like to know the diference, in price, including or not the android app.