I wrote a small python script used in a demonstration aimed at raising wifi security awareness amongst campus visitors. The script displays SSIDs sent out from the phones or other devices of people passing by. I found this script to be an useful eye catcher in awareness campaigns.
It leverages the scapy framework and is pretty easy to setup. A wireless card in monitor mode is basically all you need to get started.
This is what it looks like when you speed things up a bit:
I recommend using it together with other demonstrations, e.g. a simple
driftnet to show the benefit of encrypted HTTPS connections.
You can grab a copy of wifi-probe.py at github.