There’s now a flash “homebrew” device that works on the Nintendo DSi. It’s called the DS(onei), and it’s developed by a team called Supercard. It works like all those PSP hacks work: the DS(onei) runs a custom firmware that can be easily updated. So when Nintendo releases a game that breaks the DS(onei)’s compatability, team Supercard releases a new firmware that works again. That’s the plan, at least.
Is it the only card that works with the Nintendo DSi? I don’t think so. A quick search turned up the R4i Revolution, the Acekard2i and TTDSi. I don’t mess with the DSi like that—and I hope you don’t, too—so pardon my ignorance on this subject.
No direct links because I’m feeling noble right now.