"It's like a Fitbit for dogs," read the email in my inbox. "I'll bite," I thought. "This product could only be hilarious." I mean, a Fibit for my dog? C'mon. A few days later, with the Whistle Activity Monitor ($129.95 direct) strapped to my little Pekingese, and an app providing me insight throughout the day on when she moves around the house, I realized exactly who would pay a small sum for this technology: Anyone who hires a dog walker or relies on another person to help take care of a pooch.

A few more days with Whistle, and I totally understood who else would want this product: Pet owners who short-shrift their dogs on walks and know it and want to change it, but have never quantified it.

What is Whistle?

Whistle is a Wi-Fi and Bluetooth-enabled disc (1.5 inches wide by 0.4 inches thick) that attaches to your dog's collar to become an activity tracker, similar to modern-day pedometers, such as the Fitbit One and Nike+ FuelBand SE, yet distinctly different. The best activity trackers for humans measure how many steps you take in a day, how much sleep you get, calorie intake, calories expended, and more, giving you visibility into your habits both in any given day and over time. Whistle, on the other hand, gives you different insight into your dog's habits and health, while still telling you a thing or two about yourself. It doesn't track miles or steps—only time, duration, and intensity.

Whistle isn't about quantifying your dog's life so much as it is adding another quantifiable data point to your own life. If part of the reason you have a dog is to help you get up and move more, then Whistle is an excellent gadget for helping keep an eye on whether you're fulfilling that promise to yourself. But more importantly, it also can nudge you if you begin to notice that you're not only letting yourself down, but hurting your dog through inactivity, too.

While your pup is trotting around the house, the Whistle device connects to your home Wi-Fi network as well as your smartphone via Bluetooth 4.0 Dual Mode (Classic and Low Energy) with the free Whistle app, which is available for iOS only at the time of this writing, with an Android app due out soon. Take your dog on a walk, and Bluetooth kicks in to record the amount of time you spent on your walk together and how intense the activity was. If Sparky chases his tail for a few minutes while you're out to dinner, you'll see a little spike in his activity during that time.

The device sends updates throughout the day to your app, even when you're away from home, so you can keep an eye on how often your dog gets out of bed. My little slug of a dog, unsurprisingly, does little more than make one or two pits stops to her water bowl during the day. Because you get updates throughout the day, you can see exactly when another person, such as a dog walker, has taken your pet for a walk and for how long.

Multiple people can use the Whistle app for one dog, and multiple dogs can have profiles on one app account. In fact, when you first set up the app, you'll see Duke, the developers' dog and resident tester. You can keep Duke around and see just how wildly active he is, or nix him from sight. Each dog has his or her own settings, which account for the breed, size, and age of the dog. You can even compare your dog's daily activity to others of the same breed in the app.

Whistle Design, Specs, and Price

The Whistle device looks like a chunky disc, and I was nervous at first about putting it on my 15-pound dog. But she didn't seem to mind the weight or size of it one bit, and in fact, once I slid it onto her collar, it disappeared in her fur anyway. At 0.56 ounces, Whistle is too heavy for toy breeds to wear, however.

The company told me the size of the device comes down to two aspects of it: battery life and Wi-Fi capability. One charge lasts a week to ten days, and it recharges with an included USB cable. The Wi-Fi capability is what allows you to get updates about your dog's movement even when you're not home.

Inside the Whistle is a three-axis accelerometer, which is standard in most activity trackers for humans, too. The Whistle logo on the device has LED lights behind it so that it glows different colors to indicate a full battery, low battery, or to confirm data is uploading if you want to force it to sync by pressing its one and only button.

Whistle is waterproof and rugged. The adjustable strap that secures the Whistle to your dog's collar is designed to make sure water doesn't collect behind it and leave your companion damp. If your dog gets rough and tumble in mud, sand, salt water, or other lovely crud, you'll want to rinse it or brush it with an old toothbrush afterward.

The battery is a rechargeable lithium-ion polymer battery. And in terms of network compatibility, all you need is Wi-Fi 802.11 b/g/n (2.4GHz supported).

The price seems a bit high, but it's on par with one of my favorite activity monitors for humans, the Fitbit Force. Again, it's likely the Wi-Fi support and strong battery keeping the price above the hundred dollar mark, but those features make Whistle much more desirable than it would otherwise be.

Whistle's Sweet Song

I honestly thought the Whistle Activity Monitor would be the kind of device I'd scoff at. And while I might not personally want to drop $129 on an activity tracker for my dog, I absolutely see the benefits for people who hire dog walkers and want to make sure they're making good on their end of the bargain. It's also helpful if your family collectively take care of a dog so that you can keep an eye on who has walked the dog, who gave the pet medication or food and when (the app lets you track those things, too), and whether you're all pitching in enough. I like Whistle more than I thought I would, and I bet some serious dog lovers will appreciate it, too.