Plex for iOS and Android is just a front end, you need the server-side of the software to convert video. XBMC can convert video on-the-fly, to do this on iOS i

Plex for iOS and Android is just a front end, you need the server-side of the software to convert video. XBMC can convert video on-the-fly, to do this on iOS it uses private API for hardware acceleration (and that's why you need to jailbreak your device to install it)