Smart bra … the 'True Love Tester' bra monitors the wearer's heart-rate and pops open when she 'finds true love'.

The stakes are getting increasingly high in the battle for the weirdest piece of wearable tech. After wifi-detecting hats and smartphone-charging wellies, it was only a matter of time until it all turned to sex – with the arrival of vibrating knickers, dresses that turn transparent, and a Google Glass app that lets you imagine you're having sex with yourself.

Now, saucy Japanese lingerie brand Ravijour has upped the ante with a bra that pops open when you discover true love. Like a chastity belt for the social network age, the bra remains firmly locked shut most of the time, to defend its wearer from the hordes of sleazy menfolk trying to weasel their way in. But as soon as Prince Charming arrives, it dutifully bursts open with a gleeful spring, saving clumsy fumbling in the bedroom – and potentially taking his eye out in the process.

“When we fall in love, we experience an instant boost in excitement,” says the company's in-house Human Sexuality Specialist in the promotional video. “That feeling is unlike any other excitement we encounter in life.”

Then comes the science bit: “When excited, the adrenal medulla secretes catecholamine,” announces a man in a white coat, called Doctor. “This affects the automatic nerve and stimulates the heart rate.”

A cunning sensor built into the bra detects the wearer's heart rate and sends it to a special smartphone app for analysis, via Bluetooth. The app then calculates the “True Love Rate” based on changes in the heart rate over time. When this rate exceeds a certain value – hey-presto! – the hook opens.

“Until now, the bra was a just piece of clothing to remove,” says the smart-bra's creator, “but now it is an instrument to test for true love … destined to become a friend of women around the world.”

A friend, that is, until the bra decides to fling itself open when you're running for the bus. It might also get a bit annoying when you're watching a scary movie, if it keeps popping undone when the tension mounts. It's probably not the bra for a job interview either. Or if ever – shock horror – you want to have sex with someone you don't actually love.

As tech companies creep deeper into our homes, their eyes ever more on our bedrooms, we can no doubt look forward to bedsheets that post our performance to Facebook and condoms that send a celebratory climactic tweet. Or maybe they'll burst open too, when they can tell that you really want to have kids.