> On a related note, consider the implications of someone dropping a box like this somewhere where there's open (say, municipal) Wi-Fi and 5 V from solar power or the mains to feed it.

Last year I did a talk at BlackHat EU on abusing MiFi hotspots to do this, only using the hotspot to attack the wifi network and tunnelling back over 3G to an out of band C2. I've got a lot further since then and have working PoCs that can do this.

They're ugly, but they work and work well.