The don't need to be on a plane bit- if you end up leaving the plane once you've boarded, the plane isn't going to pull away from the gate till you're either ba

The don't need to be on a plane bit- if you end up leaving the plane once you've boarded, the plane isn't going to pull away from the gate till you're either back on the plane or everything you took onboard with you is deplaned. Now, that doesn't mean to say that you couldn't hide a bag onboard with such a device, and then make some kind of excuse that you have to go back to your office because there's some kind of emergency, and you won't be taking the flight after all. But then, you'll have had to somehow get your device into the sterile area (requiring accomplices who work there, or some surprisingly good luck getting through the x-ray scanners and explosive detection machines). In other words, the security we had pre 9/11, with a little bit of modernizing, does the job fine. The rest of it (shoes, liquids etc) are really just theatre.