Creating a visual interface for Ereadrs

I would like to create an application for an Ereader such as/or like the Sony PRS900BC Reader the application will need to know how to read a folder tree and translate it to a visual interface. It will know how to navigate using the visual interface between the folders and sub folders with addition of 2 buttons back and home. in the end of the navigation when there are no other sub folders to go to the application will open a PDF file that is in the last folder. On the second phase, after a trail period, I would like to make the app locked and not available to copy from one device to the other.