It could be argued that mobile apps are already regulated. Numerous apps have been cleared and FDA has pursued enforcement with at least one manufacturer.

What's really missing is a guidance document that spells out (especially for those who would like to avoid being regulated) the basics. My guidance wish list includes the definition of a medical device (with examples), an explanation of device classifications (again with examples), and a schedule for manufacturers to come into compliance.

A standalone app on a smart phone is pretty straight forward. The tricky bits in all this have to do with the interoperability characteristics of many of these mobile app based systems - the typical system includes one or more sensors, a data aggregator/analysis/gateway device (often a smart phone), and a backend application hosted on the Internet.

The current regulatory approach strongly favors proprietary end to end solutions. This flies in the face of a strong market preference for open system interoperability (or alternatively plug and play connectivity).

As a parallel, the FDA initially regulated PACS as an accessory to the imaging modality. Their approach has evolved over time to regulate PACS components individually as plug and play compatible components of a larger system. How quickly the FDA makes this evolution of thought in mHealth or mobile apps will have a significant impact on that nascent industry.