Specifically, GBS emulation that can be put on a flashcart and used in my DS.
I’ve been replaying Metroid Fusion and it struck me that now is the time with the DS’s controls for them to re-release Super Metroid as a portable, but since this probably won’t happen for a while I want something that will let me play the SNES rom on my DS, and since there isn’t any DS emulation I’m thinking about flash carts and the DS’ GBA slot.
So, what will let me do this? I just want to play Super Metroid. 
You can read from your flashcart on your DS right? Like, you can load DS roms onto the GBA cart and play them on the DS? Just because you have a GBA cart doesn’t neccessarily mean you can use it <i>as a DS cart</i>, you’ll need a passthrough to enable it to be read as a DS cart. Without a key you’ll be able to run only in GBA mode, meaning the extra buttons won’t be availible (which is the entire reason you want to do this).
I use the M3 passcard with my generic GBA flashcart (supermagic something, i don’t even remember), and all i have to do is load <a href=“http://www.cs.utah.edu/~tew/snesDS/”>SNESDS</a>, and a rom onto my cart. Then i put my passkey in to signal i want it booted in DS mode, and wham. Full SNES emulation.
Its not really that hard. The only downside is that alot of things on DS are specific to what cart you have. For instance, i couldn’t run New Super Mario Bros until i bought a new passkey (the M3 i’m running now). Hopefully your cart and key if you have one are compatible with SNESDS. If you want full instructions on how to setup and run SNESDS, i can PM you or something.