Bun Bun the rabbit saw his chance for freedom, and he hopped to it.

On any other day, panic would have stricken his owner, my brother Seth, as Bun Bun vanished into a thicket. The dappled bunny is ordinarily confined to a cage or outdoor pen to keep him safe from marauding predators and fast-moving cars and trucks on a nearby road.

But Bun Bun was wearing a fancy gadget on his collar that was supposed to allow us to keep track of him via a smartphone app. There was no reason to worry — until it quickly became apparent the app didn’t work.

As my brother and I discovered and many others know, a lost pet means panic, frantic calculations of direction and distance and stomach-churning worst-case fears about what might be happening to the cherished animal at that very moment. Tech companies are hoping to ease those fears with tracking devices designed specifically to help owners keep tabs on their furry friends. Unfortunately, as we found out, not all of them work as advertised.

I tested three such devices, which use various combinations of technology including GPS, cellular, WiFi and Bluetooth. The results? One clear winner, one that tracked decently enough but had numerous flaws, and one whose app didn’t work, leading to a low-tech bunny hunt.

Wearable trackers are a small piece of the $60 billion pet-products market, but they’re starting to catch on. Research firm Technavio projects 16 percent annual growth in the market for trackers and similar wearable pet devices through 2020 as the value of the segment climbs from 2015’s $890 million to $1.9 billion.

All three gadgets I tested fasten to an animal’s collar and are supposed to allow the owners to find their wayward beasts on a smartphone map. Plus, the trackers I tested allow users to set safety zones around their pet’s domestic location, and receive an alert when the animal breaches the invisible perimeter.

I put the Whistle GPS Pet Tracker on Bun Bun, and also worked with the folks at the Santa Cruz County Animal Shelter, fastening a Gibi tracker onto Darlette, a small, puffy white poodle mix, and a Pod device onto Piper, a bright-eyed terrier mix. I tracked the dogs by smartphone on their morning walk with a volunteer and a shelter staff member.

The Whistle and Pod devices also allow for monitoring a pet’s activity level, but I did not test that function.

Bun Bun, a sociable rabbit the size of a small housecat, proved a worthy test subject — he got lost faster than you could say “where’s that rabbit?” Shelter mutts Darlette and Piper also played effective roles as tracking-device quarry, ambling down to Woods Lagoon on a sunny morning. I followed them for about an hour on a smartphone, spending about a third of that time on speakerphone with a man from Gibi customer service who outlined the limitations of the device and app.

I had no problems to speak of with the Pod device. Tracking was easy, as the app showed the positions of the dog wearing the device and of the person following the dog by phone, and could refresh the animal’s location quickly, usually inside 30 seconds. Alerts about the tracking device exiting the safe zone arrived quickly.

The Pod even comes with two batteries, so the device can be kept running and charged at all times.

My only complaint with the Pod was the method of fastening it to a pet’s collar: essentially a rubbery strap resembling a zip tie. It was hard to tell if it was attached properly. The strap did the job, though, and withstood serious efforts to break it with brute force.

By contrast to the Pod, Gibi has a major flaw: when tracking on a smartphone, the location of that device — and the person using it — isn’t shown on the map, making it hard to navigate with relation to the pet’s location. While you might assume a tracking device would tell you how to get from where you are to your lost pet, that’s “not a reasonable expectation at this time,” a Gibi customer-service rep told me.

Instead, the service rep suggested that a user out tracking a lost pet should be on the phone with someone following the pet on a laptop or desktop computer “and have them give you directions to the dog.”

And the app has other annoying bugs. If any background apps are running while Gibi is up, Gibi gets bumped down in priority and the user can only refresh the pet’s location by logging in and out of the app, a company tech expert told me, adding that the firm was working on a fix.

Gibi’s “safe zone” function cleverly allows users to set a customized shape — for example the outline of a home or property. Whenever the pet leaves the zone, the user is to receive an alert.

The alert system worked, when I brought the device out of the zone. But when I left the Gibi device in the zone to mimic a dog at home, I received daily emails telling me that my imaginary pet “Rover” had left the zone, or returned to it — while the device was sitting on a table within the zone.

Gibi said this issue likely had to do with variability in GPS accuracy, but it occurred even with the safe zone set up considerably larger than the house, which is supposed to prevent the problem.

Another shortcoming: When I tried to charge the Gibi tracker, its power cord kept falling out.

In its favor, Gibi did accurately locate the dog.

As bad as Gibi was, the Whistle setup was worse; it didn’t work at all. Whistle’s app repeatedly failed to identify the device’s correct location. A Whistle customer service rep suggested perhaps a nearby refrigerator or the local airport was causing the problem, but the issue remained when I tested the device far from any airport and away from large appliances.

Ultimately, a Whistle spokesperson described my problem as uncommon and said it likely had to do with the base unit, which itself is a problem. While it’s relatively easy to change a safe zone for the Pod or Gibi device, for example when bringing the pet to someone else’s home on a visit, the safe zone for Whistle requires the base unit to be at the center of it.

A Whistle user working at the Silicon Valley Humane Society said she has two of the trackers, and they work well, after she sent one back that didn’t.

Whistle has just unveiled a new version, the Whistle 3 for $79.95, that allows for multiple safe zones and has rid itself of the base unit, relying instead on along with GPS and Bluetooth for, according to company CEO Ben Jacobs, much better performance.

As for the errant Bun Bun, all ended well. After about 15 minutes of beating the bushes, we managed to find the rabbit and return him to the safety of his pen, no thanks to Whistle. Now that we know, next time, we’ll use the Pod.

Pet trackers

Whistle GPS Pet Tracker

Mercury News rating: 2 (out of 10)

Likes: Responsive customer service.

Dislikes: App didn’t work; base unit necessary for creating safe zone; relatively large size.

Price: $49.95 for device. Service subscription ranges from $6.95 to $9.95 per month, depending on length of plan.

Gibi

Mercury News rating: 4 (out of 10)

Likes: Customizable safe zone in any shape or size; responsive customer service.

Dislikes: Loose cord/charger connection; inability to see where you are on the map while tracking; buggy app.

Price: $99 for device. Service plan costs $9.99/month or $99/year.

Pod

Mercury News rating: 9 (out of 10)

Likes: Easy tracking; compact size; extra battery included.

Dislikes: Fastener resembles a zip tie.

Price: $199 for device. Service plan is free for one year, then $49/year after.