The FDA announced their oversight of Mobile Apps and its good news for the industry, as discussed in this NY Times article.
As mobile technology has become more widespread and the power of these devices increased, there has been a proliferation of mobile apps related to health including exercise trackers, diet trackers, sleep trackers, some that are much more medical in nature and many, many others.  The concern by the industry when the FDA first announced that they would be looking into reviewing mobile apps was that the FDA might require many of these apps to go through the rigorous review process associated with medical devices.
Much of the FDA’s apparent decision-making was based upon the level of risk associated with the particular class of apps.

Many mobile apps are not medical devices (meaning such mobile apps do not meet the definition of a device under section 201(h) of the Federal Food, Drug, and Cosmetic Act (FD&C Act)), and FDA does not regulate them. Some mobile apps may meet the definition of a medical device but because they pose a lower risk to the public, FDA intends to exercise enforcement discretion over these devices (meaning it will not enforce requirements under the FD&C Act). The majority of mobile apps on the market at this time fit into these two categories.

Now developers can get back to building apps that change behavior and hopefully result in lower health risks, improved health and possibly even lower health care costs or at least a bend of the trend.
Below are some of the key points from the FDA Guidance document

When the intended use of a mobile app is for the diagnosis of disease or other conditions, or the cure, mitigation, treatment, or prevention of disease, or is intended to affect the structure or any function of the body of man, the mobile app is a device.

The FDA also said

This guidance does not address the approach for software that performs patient-specific analysis to aid or support clinical decision-making.

This will be one interesting to keep abreast of as developers begin to release apps that provide data and possible recommendations for clinical-decision making by providers.
To review the full FDA Guidance, click here MMA-1741 FDA Medical App Guidance.
And of course if you have questions about your specific app, you may wish to consult an attorney with expertise in this area.