Updating a mental list of what our phones have become today includes, but is not limited to, high street, museum, magazine, therapist, nightclub, funhouse mirror, personal trainer and abusive partner. A chilling recent addition is “crisis pregnancy centre”.

Five years ago the scandalous practices of Britain’s unregulated crisis pregnancy centres were revealed, offices where women who believed they were receiving unbiased advice and referrals for abortion were instead met by anti-choice campaigners who lied to them over tea. They said women who’d had abortions were more likely to suffer psychological damage, more likely to get breast cancer, more likely to miscarry in the future, 70% more likely to split up with their partner, and more likely to abuse their children. “There is a statistical increase,” one counsellor told an undercover Telegraph reporter. “I mean, I’m not saying it’s many people, obviously it’s still a very low percentage, but it just seems like there’s a correlation between the two.” Mmm.

Anti-choice campaigners continue to insert themselves into women’s lives uninvited, like wasps at a picnic

Truth is malleable for organisations funded by anti-abortion campaigners, and they continue to insert themselves into women’s lives uninvited, like wasps at a picnic. Sometimes they are clear about their intentions, like those who continue to “protest” outside UK clinics and film the people entering, after Sajid Javid rejected a call to create protective buffer zones around abortion clinics. And sometimes they crawl in under the door, as has been the case with the fertility app Femm, revealed last week to be bankrolled by a hedge-funder who campaigns against abortion and birth control.

To the hundreds of thousands of women who have downloaded this app and might, therefore, now be wondering when their next period is due, or indeed if: the call is not just coming from inside the house, the call is coming from inside the phone. This is the latest reminder that, despite their chatty tone, and their grateful acceptance of more than 100 million women’s monthly details of headaches, sex lives and menstrual flows, fertility-tracking apps are not our friends.

Apps have become the places where we bury all our secrets. The parts of our bodies we want to inflate, the ones we want to shrink, the age range of people we want to meet and where, and the types of sex we want to have with them and how, our legal history, the value of houses we can afford, the celebrities we spy on, the steps we have walked, how long we have slept and for what proportion of that time we snored. But the secrets don’t remain buried for long – the secrets are seeds, and they sprout, appearing again as targeted ads for kitchens and razors and ovulation tests.

Of 24 health apps in a recent BMJ study, 19 shared user data with companies, including Facebook, Google and Amazon, despite developers regularly claiming they did not collect personally identifiable information. In January, Bloomberg Businessweek reported fertility apps had raised at least $350m since they launched, in part through their use of the intimate data they collect – data we hand over with a casual click, despite the fact that apps don’t have to meet the privacy standards of hospitals. And despite the fact they don’t always get it right. Fertility awareness, promoted on tracking apps, is considered the least effective method of birth control, resulting in around 24 pregnancies for every 100 women a year. It makes such cruel sense that a pro-life organisation should choose to weaponise them.

App-creep is something most people have wondered about, whether halfway through their third night of insomnia and suddenly drowning in mattress ads, or having discussed their dying pot plants with an auntie, only to then get aggressively marketed ads from succulent sellers. Are our phones listening to us? Mark Zuckerberg says no. Is the truth, then, simply that we are as predictable as water? That a person your age, friends with your friends, logging into the WiFi at B&Q and spending £3 on a coffee, is likely to be in the market for an entry level cactus? Is the truth that we give information loosely and freely, combing over the bald patch of suspicion that it may, at any time, be used against us? I’m not sure which is more scary.

But, silver lining (well, silver-plated – it tarnishes with use), the Femm revelation is a good lesson in modern life. Like so many of our daily contemporary compromises, “what we pay in order to get something for free” is a lesson everybody needs to be educated in. An education that must be revised with every phone update. Children learn the names of every dinosaur by the time they’re three, and how to customise their Snapchat emojis by the time they’re 13. However opaque the technical details of what our phones are taking from us, surely we should have the capacity to learn the implications of clicking “agree”, so that when we choose to buy a phone, we don’t get owned ourselves.

Email Eva at e.wiseman@observer.co.uk or follow her on Twitter@EvaWiseman