Seems like a neat use for the Pi. I'd be interested to know if its CPU is powerful enough to say, crack a WEP password, in a reasonable amount of time.

Also interesting is the WiFi card the article recommends. This GitHub thread https://github.com/raspberrypi/linux/issues/369 suggests that monitor mode doesn't work with the default driver for this card provided in the kernel that's used in Raspbian etc. Does the image provided by Offensive Security use a different kernel?