Breath tracking with a smartphone - why no apps?

Question

Mobile devices

Interested in tracking breathing with a smartphone. There are developments abroad at universities where breathing is monitored through the movement of the chest (abdomen). It is determined through the reflection of the ultrasonic signal generated by the smartphone.
For example https://apnea.cs.washington.edu/apneaapp.pdf
The findings are very optimistic.
But something applications are not visible. Question - does anyone know about the pitfalls of this method?
I want to develop such a program (stress management), but the lack of ready-made applications is alarming.
PS Applications with tracking through the pulse (pressing a finger) are not interesting. Tried. The finger is uncomfortable to hold.

Answer 1

Because there is a huge gap between research and going to market.
An excellent example, about 4 years ago, an algorithm was proposed that allows you to get a 3D scan on a simple and cheap hardware a couple of orders of magnitude more accurately than is possible in principle on scanners, based on webcams and structured light .... there is a need, huge, and where finished irons?
https://habr.com/ru/company/ua-hosting/blog/388299/
web.media.mit.edu/~achoo/polar3D
And you have a very narrow area, there is no demand.
p.s. but you can fund the development of the app, since the research is already done, it might even be uplifting.

Answer 2

First, there are such applications. It was discussed on Habré. People even enjoy.
More precisely, they try to use it, because:
Secondly, they work badly.
Because:
With the help of an ordinary smartphone microphone, which, in fact, is imprisoned for the transmission of speech and only speech - even music is badly recorded through it - there is no way to get a lot of and full sound information.
And by the way, your reference is either a lie or you misunderstood
A typical smartphone does not have components capable of generating ultrasound.
At least stable enough and strong enough and directional enough plus that it does not depend on the smartphone model - definitely not.
Perhaps the researchers are hooking an additional device to the smartphone. Well, or they use an ultrasound emitter that is completely independent of the smartphone, but still external to the smartphone.