Here's a problem you probably didn't know you had: your personal security may be endangered when your portable navigation device (PND) is stolen from your car. To hear the UK Daily Mail tell it, you're at grave risk, because the Home button tells burglars where you live.

"'Satnav thieves using information stored to burgle owner's homes', warn police," says the headline of the story in the Daily Mail (It's also a problem with cell phones, the story says.) "They [burglars] then are able to make their second 'hit' on the victim—and burgle the property, knowing the occupant is likely to be out." It doesn't say how many homes have been hit in this unsporting fashion.

Take the story with a grain of salt. It claims that, "Since they went on mass sale in high street [main business street] stores last year, sat navs—which can cost up to £1,000—have become the latest 'must have accessory'." And it quotes a Garmin spokesperson who says customers should buy a sat-nav with a four-digit PIN to foil thieves. But the £1,000 price point would be just under $2,000 U.S., about twice as much as the most expensive PNDs actually cost. And there are few, if any, PNDs with PINs, although for the past year TechnoRide has been been urging GPS makers to include security codes.

If you're worried about theft, two things will help (three, if you count not leaving it attached): To a smart thief, the suction cup marks on the bottom of the windshield glass indicate the car has a GPS or radar detector (or a $3 salesman's notepad and pen kit). Every few days, take a towel and wipe the marks off. And second, instead of entering your home address, use a neighbor's—maybe the one with the hard-of-hearing German Shepherd who still has all his teeth, or the work-at-home NRA life member.