Play with a Mini-SD Adapter and see what you can find. You can crash the 3DS in whole new ways. I think I ended up finding an interesting "SDCard-canceling" mode where the 3DS will refuse to accept anything from the SDCard unless the SDCard is pulled out and then reinserted. It's quite interesting the way the 3DS will handle you taking the Mini-SD card out during a game such as Excitebike. Experiment for yourself and see what you can end up doing. I have no idea how to inject code. Much less, write 3DS ARM code to experiment with (I'm pretty sure no one, but Nintendo and it's developers do). If you find anything interesting feel free to post.