Researchers at Michigan University have made a pacemaker that runs on the very thing it regulates–the heart. Or, more specifically, they’ve created a device that harnesses energy from heartbeats and can in turn use that energy to power pacemakers.

At first blush, this seems like a terrible idea. If someone has a heart problem, is the heart the very thing you want fueling the device? But the device could work wonders for patients. Currently, those with pacemakers need to undergo a battery-replacing operation every half-decade or so. This innovation could potentially put an end to that ordeal.

“Many of the patients are children who live with pacemakers for many years,” said one of the researchers, Dr. Amin Karami, in a statement, according to The Engineer. “You can imagine how many operations they are spared if this new technology is implemented.”

According to the Daily Mail, the prototype is even smaller than the size of batteries currently used in pacemakers–about half the size, in fact.

The BBC adds that tests have shown that the device has no problem harvesting up to ten times the amount of energy you’d need to fuel the device. Even so, the British Heart Foundation wants more data–specifically, clinical trials demonstrating safety for human patients. So far, the team has only run tests that simulated heartbeats.

The technology relies on something called “piezoelectric materials.” These can generate an electric charge if their shape is changed. Some microphones use this type of technology, among other devices (see “Touch Screens that Touch Back”). 

ExtremeTech is not the only one to note the cleverness of the idea, which is a kind of “perpetual motion.” The site has also wondered in the past, more generally, whether our very bodies could be the batteries of the future.

Karami told the Daily Mail that, “What we have proven is that under optimal conditions, this concept is working.” I don’t know that that would be enough to put my life on the line. But if the device proves itself and manages to pass all the regulatory lines of defense, it could be a real boon to heart patients. And it’s a large market opportunity for device-makers, too: some 700,000 people get a pacemaker or defibrillator each year, reportedly.