Yes, even your Apple watch!
Think crystal wearing is only for hippies? Chances are you're right there with them! Albeit wristwatches are slightly less a commodity now that we've gone the way of cell phones which keep our time, schedules, photos, updates on friends' lives, dirty little secrets; they're not obsolete, thanks to fashion!
Anywho... deep inside that snazzy wrist piece (or is it time piece? that's how it's referred to in rap songs, right!?) is a quartz crystal keeping all the gears in time (*gratuitous pun alert*). Think of it like the conductor in an orchestra, keeping all the players on pace.
That is correct, a watch is not run simple by battery. In fact, the battery feeds the electricity to the crystal oscillator, which in turn, regulates the frequency of the electrode, moving the gears to drive the hands of the clock. This is how the second hand keeps perfect synchronization with the parameters we've set as a measurement of time. [Set parameters, because well, time was created by man because we need definitive standards for comfort; but that's a whole other conversation altogether] Anyways, somehow we came to a near global consensus on measurement of time (look, we can all agree on something!) and we can't have electricity acting all crazy and willy nilly messing it up. Thus the crystal serves as an energetic regulator.
Since we as humans have an electromagnetic field of energy that extends from our physical body,* it makes sense that a regulator might be helpful. I concede that perhaps the proportion of a human body mass vs the size of a tiny crystal hanging from a necklace may need greater research to prove the actuality of this, but the vast studies of the mind/body connection, placebo affect, and mindfulness can argue that the tiny crystal may additionally serve as a reminder that we have set the intention to keep our shit in line, while gently offering a wee bit of frequency regulation.
In conclusion, if you think all this crystal talk is super "woo woo" then throw away your fancy, schmancy crystal quartz wristwatch... cuz that shizz is hella woo woo!
*There is much science out there on human electro magnetic fields and peripersonal space. Check it out, our good ole friend Google can guide you!