Correct: being fertile or not is a biological attribute. It's when you introduce some means of manipulating your biological functions (either through behaviora

Correct: being fertile or not is a biological attribute. It's when you introduce some means of manipulating your biological functions (either through behavioral changes or the consumption of external substances) for the sake of your health that something becomes "medical". Your comparison breaks down: memory is a biological function, but the implements used to help one memorize stuff aren't being sold under the premise that it'll have any impact on the recipients health. With unwanted pregnancy you have the possibility of psychological trauma and physical complications -- and as with any pregnancy, risk of death. If we look at the app as just giving a rough idea of when one is ovulating, then it seems ridiculous to have the FDA involved. However, the FDA knows that people will be using this not purely out of curiosity in some biological attribute -- the app users will almost certainly be using it to choose when to have condom-less sex to not get pregnant. If the app is ineffective, it could do a lot of harm. If humans had evolved in such a way that we risked severe physical and/or psychological trauma in the pursuit of expanding our vocabulary, you can safely bet the FDA would be involved there, too.