Smealum has posted a video showing the progress he and his fellow developers/hackers have progressed on the Wii U:
Here is a quote from the videos description:
this is a video showing some of the progress we’ve been making on the wii u hacking front. this is not just my work, as it would not have been possible without the contributions of plutoo, naehrwert, yellows8 and derrek.
basically just shows some of the possibilities that come with having early high-privilege code execution capabilities; we’re able to redirect NAND accesses to SD card and run all kinds of unsigned homebrew programs. this is currently just a proof of concept, and just a week ago i was unbricking my wii u because i’d fucked up the setup. this is not in any way ready for public use, and there are currently no clear plans for release. for now, this is just the result of about a month of hard work that i felt like sharing.