Andrew 'Lizardb0y' Stephen has been tinkering with ARM-based single board computers for years. In this talk given at Kiwicon 6, Stephen details how to build your own drop box, a small device that can assist with penetration tests.
He says off the shelf products like the Pwn Plug can be expensive and others like the wifi Pineapple had limited capabilities. But perhaps his foremost motivation for building drop box was for the enjoyment of the craft.
An inconspicuous do-it-yourself penetration testing unit could be built for less than $100 with a Raspberry Pi, 3G adapter and a quality SD card.
He recommended using the Pwn Pi drop box distribution which included a "phenomenal" stack of 181 penetration testing tools like network mapping, vulnerability assessment and VoIP analysis.