None of this is malicious, said Deborah Lupton, a researcher at the University of Canberra, who recently wrote a paper documenting many of these sex-tracking apps titled “Quantified Sex.” Sara Watson, another fellow at Harvard's Berkman Center for Internet and Society, points out that many of these strange measurements come from what the phone is capable of measuring: movement and sound. “That just has to do with the reductive nature of tracking something with an accelerometer,” she said. But the apps do reflect a certain kind of bias. “I think the designers, who are mostly men are, they’re just taking up norms and assumptions that are embedded in our society about women’s fertility and sexuality, and reproducing them,” Lupton said. So sex is judged by thrusting, success is judged by endurance, and pleasure is measured in moans. “Regardless of the type of app, we should view it as a cultural product rather than something that’s just popped up out of the blue.”

If sex-tracking apps are a caricature of what straight white men think sex is, then fertility-tracking apps are a caricature of what straight white men think about periods. These apps are still designed largely by men, but now instead of sexual prowess and a Don Juan ranking, the goal is pregnancy.

Many of these invite women to give their partners access to the information. The app Glow sends a little note when a user’s partner is entering her fertile period, along with helpful seduction advice like bring her a bouquet. The vast majority of these period-tracking apps are pink. Many of them are covered in flowers. The fact that menstrual-tracking and fertility-tracking are almost always lumped together is, in itself, indicative of how developers think about women, said Lupton. “When you look at those types of apps they’re completely about the surveillance of pregnant women and making them ever more responsible and vigilant about their bodies for the sake of their fetus,” Lupton said.

Yet the appetite for period trackers is huge. And it has been huge for a long time. Seven years ago, long before apps like Clue or Glow hit the market, Heather Rivers was in college and was tracking her period using an excel spreadsheet. She thought there must be a better way, but when she Googled for period trackers she couldn’t find one. “When I didn’t find anything I decided to just make a simple weekend project version,” she told me. “Thus was born Monthly Info.” The site was simple—users record the start and end to their period and the system extrapolates from their history to guess when their next cycle will start. Trackers could set up customizable reminders, so when it was almost that time they’d get a little email with whatever message they chose.

Monthly Info was really designed for Rivers, but she added a user signup system mostly because it was easy. And people signed up. A lot of people. “It kind of took off on its own from there and grew to over 100,000 users,” she said. “There was apparently a need for something like this, because it didn’t take much energy to make or grow.” Now, there are hundreds of period-tracking apps on the market. Considering the gender imbalance in tech, it’s fair to guess most of them are made by men. Rivers joked that it’s not hard to spot a fertility-tracking app designed by a man. They focus on moods (men want to know when their girlfriends are going to be grouchy) and treat getting pregnant like a level in a video game. “It feels like the product is mansplaining your own body to you,” said Rivers, who is now an engineer working on other projects. “‘We men don’t like to be blindsided by your hormonal impulses so we need to track you, like you’re a parking meter.’”