Lost-item trackers, the high-tech savior of the forgetful, aren’t new. Attach these small Bluetooth-powered doodads to the items you fear you might lose—keys, wallet, bag, pet—and they communicate their whereabouts to your phone. Tile, one of the pioneers in the space, sells four different flavors for iPhone and Android, ranging from the $25 Tile Mate to the $35 Pro.

Samsung’s

got its $30 SmartTag for Galaxy phones. Now Apple’s bottle-cap-size AirTag for iPhone owners has arrived, and it topples the others in the world-wide game of hide-and-seek.

After two weeks of “losing” items with those trackers attached, the AirTags, in concert with my iPhone’s Find My companion app, proved to be the best. Whether it was a remote control squished between couch cushions or Wasabi, my on-loan drug-detection dog at the park (see video for that story), two unique Apple technologies led me right to them.

Yet Apple’s smallest gadget also further enables two big threats in today’s tech world: a giant company’s ever-expanding control and consolidation, and a vast, powerful network that could easily be abused by bad actors. Allow me to help you find your way.

Finding Nearby

These trackers work best when you’ve misplaced your stuff nearby, which was the case for me well before our long year of pandemic house arrest. (Yes, of course the glasses I’ve been looking for are on my head!)

AirTags and other lost-item trackers use low-powered Bluetooth to stay connected to your phone, potentially up to several hundred feet away. The strength and range depend on lots of factors, including obstacles that might come between the two. When the two are in contact, the phone’s app indicates the tracker is nearby, and lets you sound an alarm on the little disc, so you can use your ears to find it.

I scientifically tested the sounds by dropping all three of these into the Upside Down that is my backpack, then seeing which I could hear best while in a room about 30 feet away. The AirTag’s chirp, while certainly audible, was noticeably lower and softer than the Tile Pro’s melodious alarm. Samsung’s tracker was also louder—and its volume can be adjusted with its app.

Apple’s Precision Finding makes up for that weak voice. In addition to Bluetooth, AirTags contain Apple’s U1 ultra-wideband chip. If you have an iPhone 11 or later—models with their own U1 chips—you can get precise directional information about where your AirTag is located.

Tap the Find Nearby button in the Find My app when the AirTag is within close range, and a giant arrow will guide you to where to look. As you’ll see in my video, Apple can even sense when something is above you, suggesting to look on another floor. Tile and Samsung don’t have that equivalent talent.

People who constantly lose things might of course lose their AirTags—and Apple’s tag, unlike Tile’s and Samsung’s tags, lacks a handy key-ring hole. Naturally, Apple is ready to sell you a selection of holders, including a $35 leather key ring and the not-at-all-extravagant $449 Hermès luggage tag. Fortunately, third-party options are available for about $10.

Finding Far Away

But what happens now that we’re leaving our homes and losing stuff all over the darn place again? A billion iPhones help you look, that’s what happens.

When an AirTag isn’t in proximity of your iPhone, it uses other Apple devices to report its location on the Find My network. Whenever an iPhone, iPad or Mac comes within Bluetooth range of an AirTag, it can quickly connect to it and report that location back to the AirTag’s owner. This is done through an encrypted and anonymous background connection. My colleague Christopher Mims recently explained how it all works.

And it really does work. When I asked my video producer, Kenny Wassus, to hide my fanny pack with an AirTag, a Tile Pro and a Samsung Galaxy SmartTag on a public street corner, it took just four minutes for AirTag’s location to update in the Find My app via a passing iPhone. Tile and Samsung continued to say the bag was where I previously had it.

Tile has a similar connected network, but it relies on others having Tile’s iPhone or Android app. The company has sold more than 35 million units to date, spanning 195 countries. It will soon work with

Amazon’s

Sidewalk network of household devices. Samsung has a network that works with other Galaxy phones, too. Still, neither can match Apple’s instant vastness.

The most surprising test was using the AirTag as a lost-pet tracker on an adorable detection dog named Wasabi. (Don’t worry, Wasabi was accompanied by his owner and trainer, who works at the security firm 3DK9.) I equipped his collar with an AirTag and a GPS-enabled Whistle Go Explore, which uses AT&T’s cellular network to provide live location data. The Whistle app showed me exactly where the dog was headed—first on the highway and then in the park. The AirTag, within about five minutes of the dog’s arrival at the park, had picked up his location near the waterfront.

Apple doesn’t market AirTags as pet trackers. The $150 Whistle was faster, but I’d still prefer an AirTag on my dog’s collar. The Whistle requires a subscription for connectivity, plus regular battery recharging. (It’s also a canine fitness tracker.) An AirTag’s battery is expected to last a year, and you can replace the battery yourself.

What if a kind stranger stumbles upon your lost item? If you put its AirTag into Lost Mode in the Find My app, the stranger could tap it to an iPhone to see return information. But don’t count on it: Even knowing to do it, I only got it to work right by precisely holding the tag to the upper back of the iPhone.

Finding Yourself Trapped

It’s Apple’s tight control of the iPhone’s hardware and software that gives AirTags an immense leg up on Tile. Apple says it plans to open its ultra-wideband detection capabilities to third-party developers like Tile, but it hasn’t yet. My iPhone also bugs me with pop-ups saying that the Tile app is tracking my location in the background. If I want the nagging to stop, I have to disable the app’s location services, which effectively disables the whole purpose of the thing.

Those disadvantages are exactly what the 150-person company has been arguing in front of Congress. “To be clear, we welcome competition, but it has to be fair competition. Apple’s idea of competing is patently unfair,”

Kirsten Daru,

Tile’s general counsel, said last month at a Senate antitrust hearing.

An Apple spokeswoman said the company works to “help protect the privacy of users’ location data, giving users transparency and control over how all apps may access and share their location.” The company has also launched its Find My platform so other accessory makers can use the finding power and privacy of all iPhones. Tile Chief Executive CJ Prober doesn’t plan to join the Find My network because of the “unprecedented control” it would give Apple over its business. People would need to use Apple’s Find My app instead of Tile’s to find lost items, which would make the service inoperable with Android and limit the company’s ability to offer differentiated features, he told me.

And while Apple highlights its strong commitment to privacy and security, the bad actors can and will come. A small device easily used to pinpoint a dog can be easily used to pinpoint a human. And if people unknowingly have one of these on them—or hidden in their bag or car—it’d take just a day or two to figure out where they live, work or attend school.

Apple has some deterrents against using these for stalking. For one thing, if you arrive at home with an unknown AirTag, that is, one not registered to your account, you’ll get a notification on your iPhone if it’s running iOS 14.5 or later. Having an iPhone is key to this protection—it doesn’t work with Android phones. Additionally, if an AirTag has been apart from its registered owner for more than 72 hours, it will sound its alarm. But again, that alarm isn’t that loud. (Tile says it will introduce its own antistalking features for both Android and iPhone soon.)

Am I suggesting that you don’t buy an AirTag—or 25 of them—for keeping tabs on your always-disappearing important stuff? No. I’m just reminding you of the giant implications that come from using this tiny device.

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Write to Joanna Stern at joanna.stern@wsj.com