The U.S. Supreme Court recently heard arguments in the case of United States v. Jones on the constitutional limits on police use of new technology. The government argues that law enforcement personnel have the right to use a GPS to track the movements of a private vehicle without a warrant because the driver has no reasonable expectation of a right to privacy while in public. The other side of the argument is that the Fourth Amendment's provisions regarding search and seizure should protect citizens against such intrusions of privacy and require a warrant.
The case will likely be decided late next spring.