Here's my write-up watching Nintendo Wii traffic, but using ethernet port. What I do for wireless devices, is I have an extra router. I connect the secondary router to my laptop's ethernet port then my primary-router(the one connected to the modem) I join with my laptop's wifi. Then, any devices connected to the secondary-router, wired-or-wifi, will have its traffic sniffed by my laptop's wireshark/ngrep.

http://blog.sanriotown.com/minusworld:hellokitty.com/2011/02...