What a cool project! I'm working with UCSF cardiology on various projects involving Apple Watch's heart rate sensor, and here are a few applications you might consider for your technology:
1. Atrial fibrillation (you mentioned arrhythmias—this is probably the highest-impact heart arrhythmia since it causes about a quarter of strokes and is frequently undiagnosed)
2. Sleep apnea (if you can also measure oxygen saturation)
3. Heart rate variability for stress reduction or mindfulness.
4. Tracking tachycardias from Adderall usage.
5. Heart failure exacerbations (probably if paired with a scale)
6. (Perhaps) other arrhythmias like supraventricular tachycardia or atrial flutter.
7. Irritable bowel syndrome. Believe it or not, IBS is connected to heart rate variability via the action of the vagus nerve.
I'm not very up on CNN/RNN models yet, beyond the basics, but I do a fair amount of signals analysis. Is your truth data in git? I'd love to work with it. Second, did you try whitening the [audio] data prior to training your network? That might help with exposing some more salient features of your signal. Pretty neat work.
The data we used is not on our repo. It came from a database given to us by our university, and there was confidentiality issues when it came to making it publicly available.
That video was just a mock of our product. If you would like to see the results of the performance of the models, have a look at the slides we made for the project (at the bottom of the post). The best performance we got was about 0.7 r.
0.7 r is a bit optimistic I would say. We only got 0.7 for people we have been able to train on. For completely different people it learned nothing with audio spectrograms. I speculate that convolutions on raw audio would be better.
Estimation from video seemed much better. There we actually got 0.5 r on unseen people, which I find very promising.
New users don't make the front page very often, which is maybe not something to be proud of. You'll see more at https://news.ycombinator.com/newest, and https://news.ycombinator.com/noobstories if you want the motherlode. It looks like one has to be logged in to see green usernames, which I'd forgotten.
In the current case we saw CaHoop's earlier submission of this project, which got killed by an overzealous spam filter, and invited him to repost it.