The FDA's (Food and Drug Administration) key role is to protect public health by ensuring the safety, security, and accuracy of food products, drugs, cosmetics, biological merchandise, and medical devices.
Users need to be aware that just because an App references medical matters or is intended to be used within the healthcare market, it does not mean that it requires FDA approval.
Any App that the FDA has approved should note this within their App description. There are many grey areas as to whether an App requires FDA approval, so if you are ever in doubt, always contact the App developer to ask.
More information about the FDA and its involvement with medical devices can be found on their website.