Imagine that you couldn't drive on major highways without agreeing to put a camera in your car -- one that could film either the occupants or the vehicle’s surroundings and transmit the images back to a central office for inspection. You don't have to read George Orwell to conjure up such an ominous surveillance state. You just have to skim through filings at the U.S. Patent Office.

It's hard to imagine Americans would tolerate such a direct, Big-Brotherish intrusion. But they might not notice if the all-seeing cameras were tucked inside another kind of government tracking technology that millions of Americans have already invited into their cars.

Kapsch TrafficCom AG, an Austrian company that just signed a 10-year contract to provide in-car transponders such as the E-Z Pass to 22 electronic highway toll collection systems around the U.S., recently filed a patent on technology to add multi-function mini-cameras to their toll gadgets. Today, transponders are in about 22 million cars around the U.S. Adding inward and outward facing cameras to the gadgets would create surveillance capabilities far beyond anything government agencies have tried until now.

The stated reason for an inward-pointing camera is to verify the number of occupants in the car for enforcement of HOV and HOT lanes. The outward-pointing camera could be used for the same purpose, helping authorities enforce minimum occupant rules against drivers who aren't carrying transponders.

But it's easy to imagine other uses. The patent says the transponders would have the ability to store and transmit pictures, either at random intervals or on command from a central office. It would be tempting to use them as part of a search for a lost child, for example, and law enforcement officials might find the data treasure trove irresistible. The gadget could also be instructed to take pictures when the acceleration of a car "exceeds a threshold," or when accidents occur, so it could be used like an airplane cockpit flight recorder.

Kapsch sells its technology in 41 countries around the globe, and 64 million cars worldwide have been outfitted with its transponders, according to the firm's website. Occupant cameras could be attractive, and more acceptable, outside the U.S.

Tien said there's nothing inherently bad about using new technology to enforce tolls, but he cautioned against what is sometimes called "surveillance spillover." Technology designed for one function is inevitably used by law enforcement officials and other government agencies in unintended ways.

"The whole tracking thing is a bogus argument," said Wilkins. "If you have a cell phone you are being tracked anyway. Law enforcement can get to cell phone records just as easily (as E-Z Pass records). And the phone company keeps that data a very long time."