According to Nintendo-Scene, a group of modders "were able to find encryption and decryption keys by doing full memory dumps at runtime over a custom serial interface -- using these keys, they were able to create a Wii 'game' that ran their own code." Video after the break.
Someone was able to start Homebrew in Wii-Mode. The video [in English] is from a hackers event in Germany. It's mainly about the xbox 360, but at the end they speak about wii and show own Code injected in Lego Star Wars[via Wiinintendo]