Now that the company is up and running stateside, Lichtenstein says, they plan to refine the technology. The next step: adding Bluetooth wireless capabilities to the device, so that it can communicate with a cell phone or a PDA.

Companies like EKGuard are already operating in Israel, England, Switzerland, Germany, Italy, and the Netherlands. More than 120,000 people in Israel alone are using a similar service, according to Lichtenstein, and a study by one company found that the technology helped its customers cut emergency-room visits by 30 percent. Even more telling, the average time it took for heart attack victims to call for help after their first symptoms appeared dropped from four hours to around 40 minutes.

In the United States, "as many as two-thirds of patients with heart attacks don't arrive at the hospital for treatment until four of five hours after their symptoms started," says cardiologist Mark Apfelbaum, chief of the Interventional Cardiology Network at New York's Columbia University Medical Center and a member of EKGuard's medical advisory board. "And any time you cut hours off time to treatment, fewer people are going to die."

EKGuard encourages their subscribers to call at the first sign of trouble -- as well they should, if they want to get their money's worth. The service costs between $499 and $599 to start up (depending on the term of the contract), with subsequent monthly fees run $69-79.

"With this service available, I think patients will have much more of an inclination to call 10 or 15 minutes after their symptoms start," says Apfelbaum. "We can see immediately on the EKG if it is, indeed, a heart attack. We call 911, we get the ambulance to the patient, call the closest hospital, have the [catheterization] lab ready and waiting, and can shave hours off treatment time in heart attack patients."

The service will be most helpful for certain groups: those who've already been diagnosed with heart disease, who have had at least one heart attack already, who have had angioplasty, or who have other serious concerns about their cardiac health. But the company is also courting the "worried well" -- people with high risk factors, such as hypertension and high cholesterol, but no history of the disease.