Once I set everything up, the app gave Ellie a daily goal for "active minutes." Whistle says it generates this goal based on your dog's age, breed and weight; it also takes into account data from Whistle's database of pets who have similar characteristics to assign a goal. Ellie got credit toward that daily goal when we went on walks, as well as for any more vigorous activity (like tearing around the house before dinner). The app also estimates how far she traveled, how many calories she burned and how long she was resting.
I found these metrics semi-reliable. The main issue I ran into was that the Whistle seemed to overestimate how far she walked in a given day. That's because distance estimates are based primarily on the three-axis accelerometer; using the GPS constantly for tracking distance would run down the battery far too quickly. So instead it combines accelerometer data with the GPS tracking from when you're out on a walk to pull together these estimates. By default, the Whistle GPS tracks your dog's location every six minutes when not connected to WiFi; combining these points with the accelerometer data completes the estimate. In any case, my dog isn't training for a marathon, so I'm fine with trading off some imprecision in exchange for battery life.
Fortunately, I didn't need to activate the lost pet mode for real, but I did some testing to see how the Whistle works if your pet is gone. When walking my dog, I got an alert that Ellie was outside her home zone, with an approximate address. That address was usually accurate, but the alert took longer to arrive on my phone than I would have expected; we had gone a full block before the Whistle recognized she was out of the home zone.
Once that alert came through, I checked the app to see where Ellie was located when it was sent and enabled the always-on tracking to see exactly where she was. Helpfully, it also shows where you are on the app so you can figure out how to quickly get to your pet. As I mentioned earlier, the Whistle only checks in and updates location every six minutes by default to save battery life, so you're going to want to hit that always-on switch if your pet is really lost.
The main downside with the six-minute interval, aside from taking a bit longer than I'd like to send crucial alerts, is that it makes for pretty wonky walk-tracking data. After you take a walk, the Whistle app shows your route as part of the daily activity view, but that map was rather incomplete — it only shows the points where the Whistle "checked in" and puts lines between them, which results in a route that often didn't match reality.
Overall, Whistle engineered the Go Explore to use the GPS and cell radios sparingly, saving the battery for emergency situations. The good news is that this lead to tremendous battery life overall. I've been using it for nearly a month and only just saw my first low-battery warning. But with 22 percent left, I could easily use it for several more days.
Of course, your mileage will vary. Ellie's on the older side now, so she's not quite as active as a younger pup would be. She gets out of the house for two long walks a day and one or two short ones, so the majority of the time the Whistle was connected to my WiFi network, putting it in power-save mode. A few weeks into my testing, I also changed the GPS refresh rate to every three minutes, rather than every six, so I'd get more accurate tracking on our walks. Even with that change, the battery stayed solid.
Battery life is the main differentiator between the $130 Go Explore and the $100 Explore (the other is the Go Explore's light). Whistle claims 20 days for the former and 10 for the latter. Based on how long I got, though, I'd imagine that anyone with a lower-energy dog could buy the standard Explore and get longer than 10 days from it.