If you've visited someone in the hospital lately, you know that to answer a cell phone in a patient's room is forbidden. You've probably walked all the way out of the hospital to make or take a call. Just maybe, between you and me, you've surreptitiously taken a call, talking in a low voice so the nurses don't hear you.

Well, researchers at the Mayo Clinic in Rochester, Minn., say there's no need for subterfuge. The researchers tested a variety of cell phones using different technologies from different carriers and turned them on near 192 different kinds of medical devices. After 300 tests and five months, they reported no problems with medical equipment because of the proximity of the cell phones.

That should be a comfort to people with pacemakers who have been warned by doctors to use cell phones sparingly and not to talk too long when they do. Or to use them on the side of the body opposite of the pacemaker's location.

However, doctors in Tennessee have found that something most people don't think twice about—standing near the theft detection devices placed by doors in many retail stores—can cause trouble with implanted heart devices, such as pacemakers and defibrillators.

The doctors want to get the word out so store employees know what to do if someone has trouble near the entrance to a store. "Simply moving the person away from the anti-theft device may save their life," Dr. J. Rod Gimbel of East Tennessee Heart Consultants told Reuters.