I've had no problems traveling through airport security with my REOs.. most of the TSA agents I've dealt with knew exactly what it was. Only thing I did was take the battery out of the device and lay it next to the REO in the fancy gray tray they provide.
Also, make sure you either (a) only have about a third of a bottle full in your REO or, (b) unscrew your juice bottle from the device before you take off.. Otherwise you're going to have a mess on (in) your hands with the cabin pressurization.
Safe travels..