gladius has updated his page with positive progress on the DS Wi-Fi hacking front.
Very good news, I put my DS into Pictochat and managed to get to start the 802.11b authentication process. This means it will at least be possible to research communication with the DS (multiboot, tunnelling). The source to the neccesary programs is here. BE WARNED, this is highly developmental software, it's quite possible it will crash your kernel, etc. Secondly, there is really no functionality here, it's a proof of concept, I'm releasing the source to help spur the development onwards.
Update: managed to get the DS to think Mario 64 is available for wireless download - can't send it yet, and can't modify the replayed packets because there appears to be some sort of CRC check. Try out replay.c on a libpcap capture of mario 64 sending out beacon frames, you'll need at least 4-5 seconds of capture.
As always, go to his page for the full story as well as source code and hardeware/OS requirements. It's also worth mentioning that the gbadev DSDev Wi-Fi hacking thread is still going strong. I recommend you keep watching it as it contains extra minutia that might be helpful to those who are working in tandem on this effort.