How can love exist without trust? And how can trust exist without quantifiable data from a wearable fitness device that tracks your partner’s physical activity 24 hours a day?

Clip-on health trackers like BodyMedia armbands and Basis watches are gaining popularity in the tech world as a way to monitor and share fitness data with doctors, trainers, and even social media friends. Each type of physical activity produces its own unique “signature” — that is, the sharable line graph will look different when you do yoga than when you go for a run. Or when you have a sweaty romp in the bedroom.

TechCrunch‘s Gregory Ferenstein, who wears his BodyMedia armband 24/7, realized how potentially invasive these devices are after a friend who was casually looking through his data could tell exactly when he’d had sex.

“Were I married,” he notes, “my wife might like to know why I burned 100 calories between 1:07 to 2:00 am, without taking a single step, and fell asleep right afterwards.”

The implications here are pretty scary, Orwell’s Thought Police scary. Not only can a third party (like, say, a jealous spouse or overbearing parent) see when you’ve been bumpin’ uglies with someone, but they can even infer whether the device-wearer reached (or faked) orgasm.

If you thought secret email reading or phone bill snooping was bad, just imagine the possibilities these devices will offer the controlling, jealous crazies of the world if when they become part of our daily repertoire. Let’s just hope that these fitness monitoring devices remain in the realm of doctor-patient confidentiality, and that Victoria’s Secret doesn’t start making custom BodyMedia garter belts.