I was part way through setting it up to spoof as an active directory backup (or primary auth server) before we had the plug pulled.
Did two real pentests with it. Went back to the client with a list of 90% of their passwords and hundreds of web account authentication details (shopping sites, email, amazon, slashdot, etc.).
I'd love to build one again today. Battery powered and a lot smaller than what is seen in that Ars article. They would be so cheap that it wouldn't be worth retrieving - just letting them run for a week and being able to reverse shell into it to control it.
Hacking an android phone would be good for this. remove the screen and get 10+ days of battery life of just the OS running (remove bluetooth, etc.). package it as something that looks innocent of place it under carper or in a void space in a wall.
Does your $100 include 3G hardware? Or is it included in the $80 price tag that you mentioned in a different post downthread?
Does your pelican case looks as innocuous as this thing does plugged into the wall at XYZ Corp?
Do you think you could mod a vanilla openwrt installation to do the NAC/802.1x/RADIUS bypass in two hours?
Do you already have a reliable/repeatable process to get through basic corporate IPS/FW and get a reverse shell? Can you rattle it off the top of your head right now? If not its going to be tough to implement in two hours...