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Just when you thought it was safe behind the wheel of your large automobile, government attorneys are trying again to monitor your movements.

Back in 2011, the Supreme Court ruled against the Justice Department stating that warrantless GPS tracking by government authorities amounted to unreasonable search and was thus protected by the constitution. The case involved police that had monitored the location of a suspect's SUV, a modern-day version of GPS eavesdropping.

However, yesterday, a U.S. Assistant District Attorney at an appeals court hearing on a different case in Philadelphia argued that planting a GPS device on a suspect's vehicle -- without a warrant -- followed relevant legal precedents.

Disturbing as many motorists may find the idea of a GPS device sending authorities messages about their every movement without any judicial oversight, this particular case is just the tip of the potential iceberg.

A flood of data about drivers is about to be unleashed, and there are few if any laws protecting privacy in this area.

A veritable flood of data about drivers -- every turn of the wheel, every application of the brakes -- is about to be unleashed into the open market. (Some privacy advocates argue that it's already out there, thanks to smartphones.) And at the moment, there are few if any laws protecting privacy in this area or specifying how or for what purposes such information can be used.

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To give you an inkling of what's to come, today at the New York International Auto Show, Ford officially launched a new experimental program that will allow researchers to access not just basic car diagnostic data, but also details about driver behavior that was until now restricted to, well, just to the car. The idea is to help developers create innovative safety, fuel economy, and personalization features. You could be alerted that there's black ice ahead, for example, based on the information sent from other vehicles ahead of you on the road. Or a dashboard device could tell you ways to improve fuel economy (slow down and avoid traffic ahead).

No final products will come of the Ford program without the automaker's approval (a separate arrangement with the company will have to be made before any product hits the real world). However, the open source initiative -- the first of its kind -- offers a glimpse at a future in which information such as aggressive braking, rapid steering wheel turns, and wiper blade activity are all shared among commercial app developers and companies.

Drivers are very sensitive when it comes to sharing such information. There's something very personal about the American automobile, and even small perceived violations of that status are met with opprobrium. Witness the reaction from owners when GM decided to change its OnStar terms and conditions with amendments that would allow it to sell driving data to outside companies.

The reaction of GM owners was vociferous, to say the least, and GM ended up backtracking. Ford is well aware of GM's public relations missteps, and Ford representatives emphasize that the company is sensitive to these concerns. It wants to focus on safety and fuel economy, offering for example, driving tips (you didn't come to a full stop at that sign) and advice (you're accelerating too hard and wasting gas).

While the private market may be sensitive to consumer's concerns -- and any possible backlash -- government authorities need not be as receptive. They want to be able to use all available technology to thwart crime. Already, cameras in many cities and towns, such as Tiburon, California, record, track, and check every license plate that enters their municipalities. LPR or license plate readers are common, so why stop there? GPS tracking may seem relatively innocuous by comparison.

Stopping criminal activity is no doubt a laudable goal, but randomly searching every residence is not allowed. So too should the warrantless use of such digital tools to monitor our movements be illegal.

The Supreme Court decision on this issue hinged partly on people's expectation of privacy (citing an article by this reporter on the topic). We clearly do things behind the wheel (singing off-key to an Adele song or swearing like a truck driver) that we would not do in public. Conversely, the 20-something crowd that's grown up with Web cams and smart phones that record our movements and messages seems less worried about privacy. So if more people expect less privacy, could this right evaporate?

There are some bills before Congress intended to prevent just anyone, such as a private detective or security firm, from tracking you with a GPS device. The Geolocational Privacy and Surveillance Act (H.R. 1312), introduced in the House by Jason Chaffetz (R-Utah) and in the Senate by Ron Wyden (D-Ore.) and Mark Kirk (R-Ill.), would restrict such use and require warrants. It's particularly important in light of the fact that soon every car will be built with a black box that could contain a wealth of such information.

But even without legislation or court rulings, criminals will soon catch on and adopt measures to stymie police monitoring. GPS jammers are illegal but cheap and readily available, for example. So anyone with bad intent could still evade the authorities. Meanwhile, the rest of us would still be followed along the open road.

Follow John R. Quain on Twitter @jqontech or find more tech coverage at J-Q.com.