Mobile medical apps are mobile apps that meet the definition of a “device” which are intended either:

1- To be used as an accessory to a regulated medical device; or
2- To transform a mobile platform into a regulated medical device.
So, since your app will transform a mobile platform into a regulated medical device and will be used as a hearing aids, so it will be %100 mobile medical app.
Examples for mobile medical apps approved by FDA:
AirStrip ONE
AirStrip ONE is a diagnostic aid that delivers patient data from medical devices, electronic medical records and patient monitors to clinicians – in a single view on their smartphone or iPad. Clinical data includes vital signs, allergies, medications, medical images and lab results with information generated from medical devices.

ResolutionMD
This medical viewing product provides instant access to radiology diagnostic images and reports from mobile devices. The app streams data from a variety of imaging modalities, with off-site servers preparing it for rapid visualization on a smartphone or tablet. Since most processing is done outside the mobile device, no sensitive patient information seems to be transmitted, making it a fundamentally secure process.

So there you have our recommendations for the most useful, not to mention coolest, FDA approved health apps on the market for physicians.
https://www.fda.gov/MedicalDevices/DigitalHealth/MobileMedicalApplications/ucm368744.htm