Team Twiizers have just posted a DSi mode DSiWare exploit. It loads NDS binaries directly from the internal SD card slot.
Team Twiizers says:
"As you may remember we started looking at the DSi about two years ago. Despite some early attempts using savegame hacks for hybrid card games we eventually resorted to more complex attacks that involved soldering many wires to tiny points on the PCB to be able to trace and modify the RAM. However, doing this is not feasible for the average homebrew user so we used the knowledge we gained through these complicated attacks to get more information about the whole system which allowed us to experiment with DSiWare games in the end. We also learned how to create savegames so we can now do what we did three years ago with the Wii: Savegame hacks!"
Source: http://hackmii.com/2011/01/sudokuhax-release/
Original Video: http://www.youtube.com/watch?v=S2W8RNvamhI
Download: http://bootmii.org/dsiexploits/downloads/