Based on the definition you provided I do believe that the app your team developed in capstone is considered to be a mobile medical app. Your app allows for a mobile user to check their auditory cues and identify which sounds frequencies they can or can not hear. This app allows the user to check their hearing without the use of the Audiometer medical device. The app might not be as accurate as an actual medical device which test auditory cues but it can be used as a regulated medical device.
A mobile medical app that I found online is called "instant blood pressure." This app allows a mobile user to read their blood pressure in 35 seconds. The user simply places their right index finger over the lens of the camera and holds the phone against their chest to get estimates of their blood pressure. Their is also another app called "instant heart rate" which identifies your heart rate by placing your finger over the camera lens on your phone. These two apps act like a sphygmomanometer and ECG, respectively.

https://www.instantbloodpressure.com/
https://play.google.com/store/apps/details?id=si.modula.android.instantheartrate&hl=en

I agree and believe your senior project would be classified as a "mobile medical app." As you stated, the FDA did claim that "mobile medical apps" are intended to be "used as an accessory to a regulated medical device. Your app seems to do just that. Hearing aides are indeed FDA regulated medical devices and your app is being used in conjunction with that device.

There are probably a lot of examples you can find on the App/Play Store for mobile medical devices. I think I have an example of what might NOT be a a mobile medical device but could easily be mistaken as one. I have a friend whose senior project was to develop an app that is connected to a a heart-rate wrist wear such as a FitBit. The point of the App was to connect with friends or family and then you'd be able to monitor each other's heart rate. You'd be notified through the app if someone's heart rate would be too high just in case there was an emergency. Who knows, maybe your friend or family member could have a heart attack and is in a situation where he/she may not be able to get help.

Why I think this concept might not be a mobile medical app is because devices such as the FitBit itself isn't regulated by the FDA in the first place. So in my opinion, the main takeaway would be that in order for an app to be a "mobile medical app," the device that it's supporting should be a regulated FDA medical device.

https://www.bloomberg.com/news/articles/2016-04-15/fitbit-s-move-into-medical-gadgets-risks-attracting-fda-scrutiny

http://www.theverge.com/2015/6/24/8836049/fda-regulation-health-trackers-wearables-fitbit

I agree with my classmates that your application that you designed for senior project should be classified as a mobile medical app. I couldn't access your reference link, but I found two links by the FDA that completely breakdown the classification of what to be considered a mobile medical app and what not. The first link has the types of examples that would be considered eligible for their regulation. The second link states what might be confused as a mobile medical app.

http://www.fda.gov/MedicalDevices/DigitalHealth/MobileMedicalApplications/ucm368743.htm

http://www.fda.gov/MedicalDevices/DigitalHealth/MobileMedicalApplications/ucm388746.htm

-Lamiaa

Hello,
I think during capstone project the application your team developed is considered to be mobile medical app because it allows people to retain their auditory stimuli. Furthermore, mobile medical application is something that can help people manage their own health and wellness, promote healthy living, and gain access to useful information when and where they need it and your device will improve people’s lifestyle and health. FDA regulates certain mobile medical apps that are moderate-risk (class II) and high risk (class III) but I think your app should considered class I due to low risk and regulatory requirement is general control.
While searching through internet, I found the mobile medical app LactMed developed and maintained by National Institutes of Health which provides nursing mothers with information on drugs and other chemicals about the effects on breast milk and nursing infants. It also detect how these drugs impact an infant’s well-being and inform safe maternal and infant drug levels as well.
Link is provided to see which mobile medical apps that may meet the definition of medical device and for which FDA intends to exercise enforcement discretion.
http://www.fda.gov/MedicalDevices/DigitalHealth/MobileMedicalApplications/ucm368744.htm
FDA also updated App lists for mobile medical apps
https://www.klick.com/health/news/blog/regulatory/fda-updates-app-lists-for-mobile-medical-apps/

I concur with Betty that there are numerous applications exists to check pulse however those are not exact. The mercury gauges are the most precise, however, they have been eliminated of most therapeutic offices. Mechanical gauges and electronic gages are exact just on the off chance that they are frequently adjusted against a mercury gauge or through some other instrument. The mechanized gauges are exceptionally incorrect, particularly when utilized over garments, or in individuals that have overabundance fat on their arms. Thus, there's no real way to know which machine is generally exact.

I agree with pretty much everyone on this post regarding the fact that your device would be considered a mobile medical app. The fact that your capstone project actually served as a method to TRAIN users to hear auditory cues implies that it is aiding the person in a way. The FDA has a very intricate definition for a medical device but, I am going to take the parts that are relevant to your device. So, a medical device is "an instrument, apparatus, machine etc.. that is intended for use in the diagnosis of disease or other conditions, or in the cure, treatment, prevention of a disease". I think that latter part of that sentence really defines your device as it actually is trying to treat, in a sense, individuals with hearing problems. I looked at some other apps online and I found this really interesting one: AgaMatrix's iPhone Glucose Meter. This meter is like your typical glucose meter but it can actually hook up into your phone and shows you a detailed analysis of its findings. This can then be sent to your doctor in real-time. Really interesting stuff.

Just curious: Did you guys follow up on your project and try to get a patent? If so what are some of the regulatory concerns that you had to look into?

References:
http://www.fda.gov/AboutFDA/Transparency/Basics/ucm211822.htm
http://www.mobihealthnews.com/15137/fda-clears-agamatrixs-iphone-glucose-meter

I disagree and feel your application is more than a simple mobile medical app, I would consider it a rehabilitation device (conveniently packaged as an app on your phone, ipad, etc.). (I am expanding on Hiren’s post). In retraining auditory cues, your application assumes the role of a physical therapist (or, in this case, an auditory therapist) and as such is a stand-alone medical device. According to the FDA’s definition (and personal experiences), a mobile medical app only records and reports and some other, substantial medical device then does the regulating or performs the therapy, i.e. the app itself has no role in the actual therapeutic process. However, from what you have described, your application has a role because it does the retraining/rehabilitating of a user’s deficit auditory cues. As such, I cannot see your application being used without the guidance of a trained doctor or professional. That is, the user would not experience the full benefit of the application without properly, extensively knowing how to use it. My entire argument lies on the basis that deficit auditory-cues-identifying-abilities can be considered a real handicap. If they are not a real, rehabilitation requiring problem and/or your application’s aim is simply to sharpen auditory cues such as an app that increases cognitive function (“brainpower”) like Lumosity, then sure, consider it a mobile medical app.

In my opinion, I believe that your senior design product would be considered as a mobile medical app. In the week 1 lecture, we learned that Medical Device is anything that cure, prevent, or treat disease in humans. Furthermore, your device aids people with hearing loss and therefore it is considered as “mobile medical app”. After doing further research on medical apps, I found this really interesting app called “iHealth”, which measures all your vitals as well as your sleep. This device has really interesting analytics and graphs for all the vitals, which is really helpful for elderly in understanding their personal health. It is really interesting to see where technology has taken us and what the future will be?

I find this point about the Fitbit app very interesting. I myself own a Fitbit and the associated app, and this app allows you to monitor various things such as sleep patterns, physical activity, and even heart rate (if your model has that hardware). It gives the user some tools to better one's lifestyle, similar to the app the OP posted about.
Where these two differ though, I believe lies in the application of the app. The OP's app seems to be used solely as treatment almost for a disability whereas the Fitbit app is mostly for visualizing one's activity. Additionally, it seems that the OP's app communicates directly with an FDA-regulated device, which falls under the FDA's definition of a mobile medical app. Contrarily, someone with insomnia may find use with the Fitbit's sleep pattern recorder, but in the end all the Fitbit is doing is recording.

Applications whose functionality poses a risk to a patient’s safety if the mobile app were to not function as intended are considered mobile medical applications. Therefore app to retain the auditory cues is considered the mobile medical application. Furthermore, FDA states that "Mobile apps that use tools within the mobile platform (e.g., speaker) to produce controlled levels of test tones and signals intended for use in conducting diagnostic hearing evaluations and assisting in the diagnosis of possible otologic disorders (i.e., an audiometer). Possible product code: EWO (21 CFR 874.1050)."
One of the example of the Mobile medical application is MedDream DICOM which received a 510k approval recently. Its main function is to search, view and analyze medical devices.

Source: http://www.fda.gov/MedicalDevices/DigitalHealth/MobileMedicalApplications/ucm368743.htm

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

I consider that a mobile “medical” app as a medical device. If you are using that device to collect clinical data it should be considered a medical device. During my capstone project, we programmed an accelerometer and medical monitoring device. This device was connected to the user’s phone which was considered a “medical device”. In your case, you are collecting data of auditory cues. The goal of your project could be to mimic an audiometer, but make it more user friendly. However, you intend to use the phone as “medical device” to collect clinical data. It’s weird because a lot of companies such as apple, google, and samsung are in a dilemma with the FDA. Mainly because they make these phones and and watches that track a biometric data, like heart rate, step counter, how much you sleep, etc. I know the FDA is not as strict when it comes to devices like these, but they will be monitoring them closely.

After looking through the FDA's guidance on Software as a Medical Device (SaMD), which is detailed more simply on this FDA page https://www.fda.gov/medical-devices/digital-health/device-software-functions-including-mobile-medical-applications#e , its clear the FDA is being very tentative about its approval process.

From the sheer size of the market alone, it's no wonder its slow. As the FDA noted themselves, "In 2017, 325,000 health care applications were available on smartphones, which equates to an expected 3.7 billion mobile health application downloads that year by smartphone users worldwide."

But, more importantly, it's because they aren't approving the mobile device itself. They are only regulating downloadable Software as a Medical Device often from a different source or entity, not the mobile device's capabilities. Ineffectual hardware or problems integrating the mobile device's software with the mobile medical device's software upon update pose serious health risks to consumers. So, if you have a heart condition and download a heart monitor for your Apple Watch, but the Apple Watch you are wearing isn't callibrated correctly, you might miss an important reading. Whereas with a Software in a Medical Device product (SiMD), both the hardware and software of the device may have a longer history of testing and accuracy.

I believe that your app should be considered a mobile medical app based on the definition you provided. I believe this because, you said that your app allows it users to "retrain their auditory cues" and identify which frequencies can be heard or not. Though the app might not be as accurate as an actual medical device which test auditory cues, it can be used as a regulated medical device. A relatively newer mobile medical app that has come out is the KardiaMobile EKG Monitor. The product comes with a finger pad (KardiaMobile phone clip) that acts as a single lead EKG. It is able to detect atrial fibrillation, bradycardia, tachycardia and normal heart rhythms. 

Reference:

https://store.alivecor.com/products/kardiamobile