You must build a media access app for the iPhone and iPad (both resolutions) and a JAVA or FLASH based transcoding application for the PC / MAC.
The transcoding application will allow the user to search the files on the PC / MAC and make them accessible on the iPhone or iPad for viewing them streamed. The app will also allow them to save the files on the iPhone or iPad. The PC / MAC application must be capable of transcoding any source file on the PC / MAC for the iPhone 3G/ 3GS/ 4 and iPad's.
The communication will be via WIFI and 3G.