Three tries. More than two years. And roughly $150,000.

That's what it took for MIM Software to get the Food and Drug Administration's clearance for a smartphone application that physicians can use to view MRIs and other medical images.

"It was 2008 when we first tried," said Mark Cain, the Ohio firm's chief technology officer. "They didn't know what questions to ask and neither did we. . . . But at some point, they had to be thinking, 'How many more people will be lined up behind these guys?' "

His was, in fact, among the first apps cleared by the FDA. And since then, medical applications have flooded onto millions of smartphones, offering consumers the chance to check their heart rate, identify a pill in their medicine cabinet or even scan moles for skin cancer. Soon, if a firm called AliveCor gets its way, they may even be able to get an EKG by pressing iPhone to chest.

The gee-whiz factor can both astonish and alarm.

A defect in apps that essentially turn your phone or tablet into a medical device could prove problematic or even life-threatening: The app may not work as it should. For instance, what if lighting or contrast issues distort an X-ray that's viewed on an iPhone or iPad?

That's why federal regulators lurched into action a year ago, offering their thinking on how to police this vast new frontier. Just as they were putting the finishing touches on a plan, lawmakers intervened. The Senate moved to put the plan on hold after tech firms convinced lawmakers that more government oversight would stifle innovation and cost jobs.

Last week, Congress gave the FDA the green light to proceed with a push to define exactly which apps require government attention. But lawmakers also ordered the Obama administration to come up with a strategy that balances public interest with innovation in the years to come. The task is daunting, given the warp speed of technology.

It's a classic showdown between Washington regulators charged with safeguarding the public's health and a free-wheeling tech industrythat prizes agility and first-to-market bragging rights.

"There are two completely different mind-sets," said Merrill Matthews, a resident scholar at the Innovative Policy Institute. "The app people think: Where is there a need and how do I fill it? And the FDA thinks: Where is there a problem and how can I control it?"

Mobile apps, with their extraordinary reach, have the power to transform health care. Half of cellphone users in the United States have smartphones such as the iPhone or Android software-based devices, which can deliver care to their hands and potentially do so at a lower cost. Using smartphones and wireless tablets as diagnostic tools or monitoring devices could also cut back on emergency room visits.

For software developers, especially cash-strapped start-ups, there's an enormous amount riding on whether the FDA steps up enforcement — and exactly how it plans to do it, industry analysts said.

"The FDA approval process adds months, if not years, and potentially millions of dollars to what it takes to bring a solution to the market," said Liz Boehm, a director at ExperiaHealth, a consulting firm. "That development process would put many of these guys out of business."

Medical apps exploded onto the scene in 2010 and have grown by about 150 percent each year since, according to MobiHealth News, which tracks Apple's iTunes store, where many apps debut. Consumers can choose about 13,000 of these apps; 5,000 more are marketed to medical professionals.

The offerings range from very basic — and free — apps that calculate body mass index to more sophisticated ones that make use of pricey supplemental devices. The pharmaceutical firm Sanofi has an app for diabetics that registers glucose levels with the help of a meter that attaches to iPhones. IHealth offers an app that records blood pressure using a cuff that plugs into an iPhone, and WiThing has one that tracks weight and body-fat percentage using the company's WiFi-enabled scale.

A survey by the Pew Internet Project found that 11 percent of adults with cellphones downloaded an app last year to help them manage their health. That same year, the mobile health-apps industry generated an estimated $718 million worldwide, seven times more than the previous year, according to Research2Guidance, a consulting firm.

While the FDA currently regulates certain medical software, the agency wants to update its thinking now that smartphones have juiced the apps market.

A year ago, the agency proposed policing only a subset of those apps: ones that use supplemental attachments to transform a mobile platform into a medical device (such as AliveCor's EKG app) and others that act as accessories to an already regulated medical device (such as MIM Software's app).

Rather than overseeing all medical apps, agency officials said they want to limit regulation to a slice of the market and take a pass on low-risk apps, such as calorie counters, according to Bakul Patel, an FDA policy adviser.

"We are taking a proactive step by saying that from the FDA perspective," Patel said. "We're not concerned about all those other apps."

Software makers, on the other hand, see an agency that currently regulates next to nothing in the mobile apps space taking a sudden interest in regulating more. The FDA proposal, they say, is vague and leaves many questions unanswered. For instance, given that apps can be updated daily, does a software developer have to seek FDA approval for each update?

Among the critics is a group called the Health IT Now Coalition. It represents health-care providers, patient advocates and health insurance companies, including Aetna, which last year bought iTriage — an app that helps consumers evaluate medical symptoms and find the proper care.

"The issue here is that they're really using a process for approval of these mobile apps that was basically created when the 5 ¼-inch floppy disk was the latest technology," said Joel White, the group's executive director.

Dirk Hobbs, chief executive of Medical Voyce Sciences and Multimedia, said the FDA's plan is ambiguous and he doesn't know whether the apps his firm is developing would be regulated. The apps aim to speed communication among medical professionals in different facilities.

"This is just going to slam the brakes on an innovative sector that includes tons of small businesses like mine," said Hobbs, who expressed his concerns to Sen. Michael F. Bennet, D-Colo.

Bennet and Sen. Orrin G. Hatch, R-Utah, wrote a provision, inserted in a broader FDA funding bill, that would have delayed the FDA proposal by forcing the agency to first reach agreement with other regulators about how to handle these apps.

This week, in a compromise reached by House and Senate lawmakers, Congress allowed the FDA to press ahead. But it also directed the agency to work on a report with other regulators that would lay out an appropriate framework to promote innovation and protect patient safety.

Former FDA deputy commissioner Scott Gottlieb, who researches medical trends as a fellow at the American Enterprise Institute, said he's disappointed. If consumers can track their blood-sugar levels using pen and paper, he said, why should the government have to clear an app that does the same thing more reliably?

Gottlieb said that software developers should be suspicious because regulators have a tendency to tighten their grip on industries as they develop. "If they perceive a power vacuum," he said, "they'll step in and regulate more and more."

Some in the tech industry do not perceive a threat. They say they've been expecting the FDA to regulate some apps and are eager for the agency to reveal which ones.

A group called the mHealth Regulatory Coalition — which represents established firms such as Qualcomm as well as start-up software developers — was formed in 2010 to deal with mobile health care regulatory issues. Its leaders argue that uncertainty breeds anxiety and drives away potential investors.

"We started telling the FDA that they're going to stifle innovation if they don't start clarifying where the lines will be drawn," said Bradley Thompson, the group's general counsel. Other technology groups — including the West Wireless Health Institute and the Application Developers Alliance — have taken a similar position.

In a recent meeting with industry representatives, Jeffrey E. Shuren, head of the FDA's Center for Devices and Radiological Health, assured the group that the final plan would include more details than the draft, some attendees said. The agency may even create a Web site with generic examples of apps that would be exempt, Shuren told them.

In the end, the FDA's plan may indeed sink some software makers whose products can't withstand federal scrutiny, said Lisa Suennen, co-founder of Psilos Group, a health-care-focused venture capital firm.

"But while regulation puts an extra burden on young companies, those that can get through it will have a huge competitive advantage," Suennen said. "You can't have every Tom, Dick and Harry claiming that their medical app adds value without having to prove it."