I built a similar device myself, following instructions given at [1]. Very handy little device, for multiple non-malicious reasons. I can carry a wireless router, power supply and cable around in my jacket pocket, and you can do fun stuff like telling the wireless router to transparently send all traffic through something like OpenVPN (or Tor, if you're paranoid). Makes security in potentially hostile environments very straightforward.

[1]: http://www.minipwner.com/