The comments on this post are interesting: 1. Some insist that the source code be made public. 2. Some insist that there be no in-app purchases. 3. Some insist that there be no analytics whatsoever. Each of the above has some legitimate reason. However, do privacy-focused apps need to play by different set of rules? If so, what special monetization models would make sense to folks on here? #AskingForAFriend
Period tracker app is something a programming student can do. (Maybe with some questionable choices resulting in potential data loss, but this can be fixed.) You don't need a degree to make basic cycle prediction, and you can't reason about anything else without real medical knowledge. So this is something that can be done once in open source, and put onto F-Droid for everyone to use (and, of course, it already has such apps). Something as simple as calculator does not need “cloud account”, nor internet connection at all.
But how are we going to make money on that? How do we grab data that can be sold from users?
So the snake oil festival starts. From cute backgrounds to “AI advice”, lots of nonsense gets invented to grab and hold user attention, and hordes of paid biological word generators pretend that they have never felt “safe” before using “this app”. Many choose to directly ask for sex and pregnancy planning data to be sure they are the first who can sell it. Everything is done to smoke-screen the fact that users are only needed to input as much data into the machine as possible.
“Privacy focused” is just one of such fake labels. It means “we will try hard to protect any data we can sell from other bastards who want to do the same”.
Needless to say, little data brokers just follow the example of platform owners who run the circus, and dream to become data mafia kingpins one day. They benefit from each other, so you won't find simple apps with no strings attached being recommended by the app stores, because they are Bad for Business™.
As for third party “analytic solutions”, in simple terms, you simply let them collect some data on your users to get some charts and generally useless information (useful information costs money — sometimes a lot of money; each time Google or Apple decide whether they should do X or not, it costs Facebook a large sum, and new agreements behind closed doors).