NOTE! the "R4 Ultra" is simply an R4 clone. it does support more space, and it can be configured to work with the DSi, but it's a pretty shoddy copy of an R4. a lot of games don't work on it. it might be worth it (it is only like 6 dollars afterall) if you just want to use it for homebrew, i guess. but make sure you do some research on it to see if its what you need, because it's definitely not as good as an original r4 (which is hard to find these days).
Yeah, I'm trying to stay away from that one. Supposedly the people who make the real R4 are extremely pissed about this clone and are threatening to brick anyone's DS that is using one of these.
Quote from Mwgamer.com
"Yesterday on July 3rd, The Team behind the R4 flash Card for the Nintendo DS announced that in a future update. They plan to brick Nintendo DS ' that are using a Clone of their popular R4 Flash card. The compnay states that they will not warn us when it will happen. They will not warrenty any bricked NDS', Anything that happens to you NDS will be at the fault of the company that sold you you're clone flash card."
Anyways, I've been reading about a card called the M3DS Real. I think I'm going to go with that.