These are small tattoos that you stick on your arm. When you want to unlock your device, you tap it on the tattoo and it unlocks. This is supposed to be simpler than typing a password. Let’s see if it really is. Dan Seifert at The Verge bought a pack and tested them:

It’s a neat parlor trick and amusing to show off to others, but practical use is limited. The phone will only recognize the tattoo when the screen is on, so you either have to press the power button before tapping or rely on the Moto X’s motion sensing to wake the screen up when you pick up the phone. The whole process actually takes longer than just typing my PIN or drawing my swipe code. It also requires two limbs to accomplish, whereas the traditional methods can be easily done with one hand. That’s not to mention that you need to set the whole thing up again every time you replace the tattoo on your body. Unless I specifically thought about using the tattoo to unlock my phone, I quickly forgot about it and would use the other, more traditional methods most of the time. Old habits are hard to break, after all.

Not surprising that it is bad.