Iltifat Husain has seen an awful lot of sickness and injury during his time as an emergency room doctor, but lately, he's worried about something new. He's worried about the ill effects of mobile healthcare apps.

There are hundreds of medically themed apps in Apple's App Store and Google Play, and by most accounts, they've been wonderful tools for tracking, evaluating, and taking control of our personal health. Husain loves apps such as Draw MD, which lets physicians draw out surgical procedures for patients, and MicroMedex, a prescription drug reference encyclopedia. But he's concerned about the emergence of untested apps that are marketed as replacements for legitimate medical equipment—apps such as Instant Blood Pressure, which purports to take your blood pressure by way of the iPhone.

According to Husain, a faculty member in the Emergency Medicine department at the Wake Forest University School of Medicine, these apps could very well land someone in his E.R.—and maybe even get them killed.

He's not alone in his concern. With an editorial in The New England Journal of Medicine last week, Nathan Cortez, an associate professor of law at Southern Methodist University Dedman School of Law in Dallas, Texas, called attention to this problem, and you'll hear much same complaint from Eric Topol, a medical doctor and director of the Scripps Translational Science Institute. "These apps have no validated data compared with accepted reference standards and therefore are quite concerning," he says.

Although Husain believes these apps could be seriously harmful, the good news is that the FDA says it is now working to crack down on questionable healthcare apps, and some app makers may be willing to provide additional disclosures about their software when pushed to do so.

To illustrate his concern, Husain points to Instant Blood Pressure, which claims it can take a blood pressure reading in under a minute "using only your iPhone—no cuff required." The $3.99 app has been among the top 30 most-downloaded apps in the Health and Fitness section of the App Store for the past few weeks, and it features several glowing reviews. According to the app's description, it "uses a patent-pending process developed by a team from the Johns Hopkins University—a world leader in health innovation."

Screenshot: WIRED

The problem is that doctors like Husain have no reason to believe it actually works. There is no public research explaining how the app operates, and the company hasn't done the kind of study that the Food and Drug Administration would require in ordered to get Instant Blood Pressure cleared as a medical device.

We contacted Johns Hopkins about the app, and they told us that it is not affiliated with the university and that they were sending the app's maker, Aura Labs, a cease-and-desist letter demanding that they stop using their name. Husain is worried that someone might put off necessary medical treatment because of bad data obtained from an app like this. Based on the App's reviews, at least some of the users believe that they're getting accurate blood pressure measurements from the app. "Reading these comments is harrowing," Husain says. "It's like: 'Oh my god, people are actually using this stuff and thinking it's real.'"

>According to Husain, they could very well land someone in his E.R.—and maybe even get them killed.

To use Instant Blood Pressure, you download the app, press your phone against your chest, and put your index finger against the camera, and in less than a minute, it gives you a reading. I tested the app and got a 125 over 66 reading with a heart rate of 55 beats per minute. Then, after two misfires, where the app couldn't get a reading and told me to try again, it recorded 121 over 65, with a much higher heart rate of 74. At no time did the app itself warn me of its untested and potentially unreliable nature. In fact, if I hadn't scrolled down to its App Store description, and clicked "more," I would never have seen the company's warning that the software is for recreational use only and is "not an FDA cleared medical device."

The App Store description for Instant Blood Pressure, which doesn't clarify that it's not an FDA-cleared device until you click 'more'. Screenshot: WIRED

There's another app, called Instant Blood Pressure Pro that makes identical claims to Instant Blood Pressure. The app's support page appears to be inactive and provides no way to contact its maker, Mini Touch. Its lone customer review begins: "You could kill somebody."

Like other similar apps in the App Store, Instant Blood Pressure contains a disclaimer that it is for "entertainment purposes only," but this disclaimer is not immediately visible when you look at the App in Apple's store or Google Play. But there is a more prominent warning on the app's website.

A third app, called Pulse Oximeter Pro, claims to be able to measure "blood oxygen saturation without peripherals." Clicking on its support page link takes you to an Arabic-language gaming site. Yet another product, Pulse Oximeter, contains a similar, hard-to-find disclaimer, but connects to a legitimate product support site. That kind of buried caveat is simply not good enough, given the risks of medical harm here, says Topol. "The disclaimers are grossly inadequate; consumers don’t read this buried information."

Pulse Oximeter's creator, a Norwegian family medicine doctor named Damoun Nassehi, told us that he plans to add new warnings in an upcoming version of the app. And that's a good thing. According to Nassehi, his app is not always consistent and should not be used for real medical data-gathering. "It is meant to be used by adults in recreational setting," he says.

>'Our typical approach would be to allow a firm to come into compliance voluntarily before taking enforcement action.'

The FDA would not comment on any specific app, but in an email, Jennifer Rodriguez, an agency spokesperson, told us that "the FDA is focusing on a small subset of mobile apps that are medical devices and present the greatest risk to patients if they do not work as intended. For that subset, the FDA might take action were it to determine that an app does not meet relevant regulatory requirements. But our typical approach would be to allow a firm to come into compliance voluntarily before taking enforcement action."

Instant Blood Pressure's maker, Aura, company didn't respond to multiple requests for comment. But Husain claims that the company's CEO, Ryan Archdeacon, wouldn't tell him how the app worked. "He was very straightforward with telling me that he could not explain how the app works—basically stating how it’s a patent-pending process that he can’t get into at all," Husain wrote in a blog post about the app.

Now that the FDA is investigating, it will most likely work with app makers to ensure that they post adequate warnings on their unproven software. When products like these are intended to measure vital signs, they need to first be cleared by the FDA before they can be sold in the U.S., says Christopher Rush, a former FDA investigator who is now president of FDA Quality and Regulatory Consultants. And with these "recreational" medical apps, the FDA is going to take steps to ensure that consumers aren't misled into using them for medical advice. "They're going to ask the software developers to stop selling it until they get those warnings in place," he says. If that doesn't work, the FDA will most likely go straight to Apple and Google and ask them to pull the apps.