Showing Nintendo's CardsI was watching the excellent Justice League Unlimited episode "Dark Heart" written by the incomparable Warren Ellis (Transmetropolitan , Planetary) when I saw a commercial for a toy which uses some small media cards that strongly resembles the DS media. The Mattel Megaman PET with it's "battle chips" apparently uses these cards in a sort of digital trading card game mechanic.
Some mention has been made of the similarity between DS cards and the media for one of Mattel's other gizmos - a $60 personal media player called the JuiceBox. And why shouldn't there be - both cards are made by the same company: Matrix Semiconductor. Add the Megaman PET and we have a nice little selection of potential media for DS hacking.
Straight off - let me say that these cards are not directly interchangeable.
However, that having been said - it may be possible to convert or adapt either the Mattel Juiceware or the Mattel Megaman PET to a DS-readable form factor because they share the same underlying technology.
What makes these media more desireable for hacking than just cracking open an existing DS card? (Assuming that you're the kind of monster that would willingly destroy a working DS game card.) Firstly, they're cheaper and easier to find. Secondly...
...one product already exists which bridges the troublesome gap between PC and card. This JuiceBox Juicebox MP3 starter kit includes a blank 32MB card, software, Flash card adaptor and USB card reader/writer.
I have not examined this product, but varying sources claim that the media is SD. I doubt this, but don't have any trouble seeing how that rumor would get started. Any of these media would fail "The Grandma Test." IE: circle a picture in the Sears catalog of a "Mario 64 DS" and expect to see Juiceware's 30 minute episodes of "Ed, Edd and Eddie" under the tree...