Using a legitimate USB charger. The GSM radio for 2G internet broadcast. The built in battery for short term unplugged continued sniffing. Trigger word SMS messages. Live streaming web portal.
That is very, very cool. This is the kind of stealth monitoring device people just would never think to check and could easily be replaced without the user being any the wiser.
This is a beautiful example of a real hack superbly executed. Bravo.
Edit: Just realised this is the guy (or team?) behind EverCookie.