A friend of mine brought to my attention that OnStar, GM's auto navigation and communication service, will be
collecting complete speed and location data for its users, even after users cancel their service. They've also added a provision to their privacy policy allowing them to sell the data, and specifically mentioned the interest of state users in that data.
That, of course, raises all kinds of legal concerns. In the article linked above, author David Kravets rightly points out the value of that data in criminal and civil cases, as well as the more remote possibility of mining the data to issue traffic citations. When the car's owner or driver is the defendant, that would certainly seem to challenge "The right of the people to be secure in their persons, houses, papers, and effects."
But this isn't really a technology problem. If that data was stored on something like a flight data recorder in your car—and it in fact is in most newer cars—the Fourth Amendment uncontroversially protects it. Probable cause, in most cases supported by a warrant, would be necessary to use the data in a criminal case. The reason is simple: you own that data.
Here's where OnStar's policy becomes a problem: they own the data. Like most software and services, the driver of the car does not "own" the OnStar system; the software and right to use the service is licensed from OnStar and the service is bound by its terms of service.