Unregulated and potentially inaccurate apps may be used by Americans to measure their blood pressure, receiving information that could be dangerous, Reuters reported on Wednesday.

The top roughly 100 apps for hypertension and high blood pressure that are available on the Google Play and Apple iTunes stores were analyzed by researchers. They found that almost three-quarters offered tools to track medical information.

But seven Android apps that said users only had to apply their fingers onto the phone's touch screen or camera to find out what their blood pressure is. This is a claim that scientists are saying is completely inaccurate.

"This technology is really in its nascent stages, and it's not quite ready for prime time," lead author Dr. Nilay Kumar told Reuters Health.

Kumar said he was shocked to find out that these smartphone-turned-blood pressure-devices had been downloaded as many as 2.4 million times.

"That's concerning that such a small number of apps have been downloaded so many times," he said. "We were surprised by the popularity."

Though he is unsure how the technology works, he said a finger pulse is read by the phone camera.

"It's really in a research-and-development stage. It's not ready for clinical use. For now, we need to be careful that we are not using things that are inaccurate and could be potentially dangerous," he said, according to Yahoo.

The U.S. Food and Drug Administration has not given the green light to the apps, though they regulate certified medical devices.

"The idea that you're going to be able to stick your finger on the camera of your smartphone and get an accurate blood pressure reading is pretty far-fetched right now," said Karen Margolis, an internist and director of clinical research at HealthPartners Institute for Education and Research in Minneapolis.