PS1 would be easy, after all there is one on the iphone. PS2 possible but difficult. PS3 impossible or at the very least heavy slowdown.
Personally, I would like to see so code or a exe first, that video could easily be faked so I like evidence. Although I must say this is possible and definitely would bring the homebrew scene possible.
Only problem with XBMC though is that it would have to be largely rewritten and unless there is someone dedicated to it, I don't see an official port until there is a sufficient userbase....which I also don't see until we have a XBOX 1 style easy softmod which is also XBL safe.