Will Magic Lantern run on a Wireless (Wifi) SD card on a 5D Mark III?
Not recommended at all. Older Eye-Fi seems to work, newer not at all. No reports for other brands AFAIK.
And performance difference might be a non-issue: SD-card interface in 5D3 is limited to about 21 MByte/s for write operation.
The worst part is that you may have to uninstall ML first before inserting a wireless card. Nope, it is not sufficient to insert a "clean" WiFi card because a cam with bootflag enabled messes up with those cards.
If you are aware of these issues you might give it a try and report back.