With the ignition based DVD-players this would work. but from the article it uses the GPS to figure out if you are moving, so you could block the antenna if you wanted to watch your family guy, but you couldn't switch over to mapping very quickly.
The instant debit you are speaking about comes from merchants use of automated clearing houses. essentially turning your check into a direct deposit into their account from yours. when you or I deposit a check into our account, we don't have a fancy ACH machine to run the check through, so the check needs to clear in the usual way.
USB keys are also available in rather easily concealable form factors. such as the 4Gb, smaller than a stick of gum, usb key I have in my hand. which I could easily conceal even if I were naked.
An anonymous reader sends us to the site of Science Magazine for news that will interest those who have followed experiments to slow and stop light. Research groups in Canada and Japan have succeeded separately in storing a special kind of vacuum — a "squeezed vacuum" — in a puff of gas and then retrieving it a split second later. Such experiments might lead to advances in quantum encryption. At the very least they will help to illuminate the boundary between quantum and classical realms.