If you've got a defibrillator implanted in your chest, it's not an idle question to ask whether it's in good working order. Thanks to medical-equipment maker Medtronic, heart patients can check up on the lifesaving device simply by waving a mouselike wand over their chest. The wand is plugged into a standard phone jack to send data to a physician over the Internet. An implanted defibrillator a miniature version of the electric paddles that appear regularly on ER can shock a racing heart back to a healthy rhythm. But every few months, doctors must check to see if it is operating correctly. This used to mean a visit to a heart-rhythm expert. Now, with Medtronic's dial-up technology, a virtual checkup takes 15 minutes or less. The company expects similar technology to be available for pacemakers devices that speed up a sluggish heart by early next year.