What about Plex? IIRC it's a fork of XBMC and has been available for both iOS and Android for the last 6 months or so. Nothing against XBMC but Plex is probably a better choice right now if you want something stable.
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)
Unfortunately, Plex is very slow - it requires much more powerful hardware than XBMC does (the PC version, that is - haven't tried the iOS version, and I couldn't get the Android version to work)
