I have been thinking about building a privacy-first tracking app for years now.
Someone already did that with drip.: https://bloodyhealth.gitlab.io/
Maybe you would like to contribute?
Please, make sure it's available on f-droid as well, just being there means it's more trustworthy.
The problem is that stuff like privacy and open source don't attract the vast sums of venture capital that ad-selling businesses do. Sure, an average dev could probably build a working app like that - but could you ship the same quality as someone who can afford to hire an entire UX team?
Probably… it would not make you sit through 30 seconds of ads so that would be a great UX improvement.
Never mind quality - how can you achieve the same reach as someone with an advertising budget?
No, but people don't care about UX perfection in comparison. Usually it just needs to work and not get in the way.
imo, the real problem is that you need to consistently ship. It you made a one-off app then it's going to get de-listed for not being updated despite not needing an update.
I make one! It’s called Reflect.
https://apps.apple.com/us/app/reflect-track-anything/id64638...
Seems too nerdy for the market at large - the correlation etc. features might well be as good as or better than what the likes of Flo provide, but people will have a harder time understanding that than simply 'your next date is expected to be x', 'your cycle is typically x days', etc.
We definitely cater to a niche that wants to know the nitty gritty details. We’re trying to layer the app such that you get the TLDR first if you want, and can zoom into the details of why second