GPS devices in motor vehicles tell you where to turn to reach your desired destinations. But those new-fangled gadgets can also tell strangers where you're going - and where you've been.
So virtually all U.S. automakers - 19 of them - have agreed to a set of "principles" aimed at protecting Americans' privacy.
Those guidelines, recently specified in a letter from auto company executives to the Federal Trade Commission, include assurances that the information from car and truck computers won't be shared with law-enforcement authorities without a court order or sold to insurance companies.
Another pledge: Your driving data won't make you a target of advertisements for businesses along your usual routes - unless you agree to let them know your movements.
Still, as The Associated Press reported: "Information on where drivers have been and where they're going is continually sent to manufacturers when the systems are in use."
That can be beneficial when your location prompts warnings about traffic snarls and weather dangers.
But it can be creepy to realize that somebody somewhere is tracking your movements.
As for the potential emergence of GPS screens as a brave new advertising world, drivers already have too many distractions from keeping their eyes on the road.
Meanwhile, though the automakers assert that their statement of principles averts the need for "restrictive" legislation, Sen. Edward Markey, D-Mass., has this even better idea: "I will call for clear rules - not voluntary commitments - to ensure the privacy and safety of American drivers is protected."
And as Marc Rotenberg, executive director of the Electronic Privacy Information Center, told the AP:
"You just don't want your car spying on you."