Hi Colin, I agree that the IP addresses might change (and most likely they do), but my comment was not about IP addresses but about MAC addresses and MAC addresses are fixed.
Oops, yes, sorry. Your observations agree with mine.
MAC addresses are not always fixed. I seem to remember this is optional on iOS. Not sure about Android. It is indeed a security feature and is very good to turn on if you regularly connect to non-trusted WiFi networks.
I run an arp scan every few minutes using a custom lookup table containing known devices and additional known manufacturer types. The first 1/2 of the MAC address is assigned to a manufacturer so even if you don't know the address, you can often work out the device.
But none of these lookups are very reliable. Good enough for casual use though.
I think that the fingbox device is doing something very similar. I would not be amazed that under the hood it is running the arp-scan command on a unix environment. So I would also guess that a raspberry pi could perfectly do the same things.
It is also mentioning on this page that it is using arp spoofing to block users (seems like a cool - but also evil feature 
).
