Just a question, since the Topic was made in Aug 2nd, 2011 and everything about HeartGold seems to be from 2011.
Right now there are Flashcarts who run on 3DS, like DSONEi or DSTWO.
Even so, is still impossible to backup a HG using a 3DS, a Flashcart and the Original Pkmn Cart? (Not using external hardware, just software)