My solution has no hacks, no wire stripping, no electrical tape, and no re-flashing of firmware to enable injection capability... only some dollar-store velcro to hold everything together. Entirely off-the-shelf parts, including the USB OTG adapter. OK, so it's a fairly specific shelf that it comes off of, but you don't need that one, you can just use the standard cable the N8x0 comes with and the USBControl package.

My primary use for the battery/hub setup is to be able to use multiple USB devices on my N800 simultaneously (for copying pictures off of my camera onto my USB memory stick, for example) but it also works for this purpose too. The Asus Wifi adapter was $25.

The battery pack also has adapters to charge / power other stuff. I can use it to run the N800 for 8+ hours, perfect for watching movies on long flights or backcountry GPS tracking. Even better, it just takes 4 rechargable AA batteries, so I can carry an extra set and swap them when the first set wears out.