Finger-chilling winters and modern smartphone screens don’t mix. Capacitive touch-screen phones can only detect skin-to-glass contact, which is why every year, the market is flooded with touch-screen-compatible gloves–woven with a special kind of capacitive thread that tricks touch screens into thinking a finger is naked.

But with the rising ubiquity smartphones with fingerprint sensors, a new cold-weather problem has revealed itself. Fingerprint sensors, like capacitive touch screens, won’t work if you’re wearing gloves. And on iPhones, at least, where TouchID is integrated into everything from logging in to buying apps, that’s a surprisingly irritating limitation.

Tony Yu thinks the solution is Taps, a bizarre new accessory that is essentially a tiny synthetic fingerprint you can stick to any glove, tricking your smartphone into thinking it’s one of your real fingers.

Like touch screens and trackpads, the fingerprint sensors in smartphones like the iPhone and Google Pixel measure capacitance. When it comes to touch screens, a uniform electromagnetic field is created on the surface of a grid. When a finger touches the grid, a computer can tell where it is according to how much that electromagnetic field deforms, and where. For capacitive touch screens and trackpads, this grid is actually pretty low-res, which is why most touch screens can’t read more than, say, 10 fingers at once: a computer’s only trying to figure out where a finger is and how it’s moving, not what it looks like.

On fingerprint sensors, though, you’ve got a much higher resolution packed into a much smaller area, so that the sensor can actually detect where the individual raised ridges of your fingerprint are touching the glass.

The similarity between the technology of fingerprint sensors and touch screens is why it’s likely we’ll see fingerprint-sensing touch screens in the coming years. It’s also why Yu–who in 2014 founded a company called Nanotips around technology that makes any glove touch-screen compatible–realized that there would be a growing market for gloves that were fingerprint sensor-compatible.

Taps isn’t a high-tech solution to the problem, but it is effective. It’s essentially a fingertip-sized sticker made of military-grade polyurethane that you stick to the end of your glove. It’s capacitive, meaning a touchscreen thinks it’s a finger, but thanks to a subtle, unique ripple pattern on the tip, a fingerprint sensor also recognizes it. To use Taps, you train it to recognize the pattern of this sticker as if it were any other finger on your hand; then, when it’s cold outside, your glove works to unlock your smartphone, just as if it were a third thumb.