The FitBark and Whistle are both dog monitors. While the FitBark is geared particularly towards activity and health tracking, the Whistle is geared towards GPS tracking as well as activity. They definitely do have some differences and it really depends on you and your dog as to which one is a better fit.

The FitBark is a very lightweight, easy-to-use dog activity monitor. It’s simple to charge, simple to see stats, and it has an attractive bone shape design. It shows “BarkPoints”, sleep scores, and calories. You can even see your dog’s stats from the last week or month at a few taps! To learn more about the FitBark, click here.

The Whistle is both an activity monitor and a GPS tracker. This means that the location of your pup is always right at your fingers! A GPS tracker is useful for dogs who tend to explore past the fence without your knowledge. The Whistle also does track activity like the FitBark. To learn more about the Whistle, click here.

Here is the FitBark vs. the Whistle lowdown:

Fitbark Whistle
Size The FitBark is considerably smaller than the Whistle and is less likely to get caught on things or bother the dog. Weight: 0.28 oz SizeThe FitBark is considerably smaller than the Whistle and is less likely to get caught on things or bother the dog.,Weight: 0.28 ozThe Whistle is slightly larger than the FitBark and may not be comfortable for very small dogs. It also may be more noticeable than the FitBark. Weight: 0.92 oz
Colors The FitBark comes in seven different colors, including "Free Spirit Green", "Partner in Crime Black", and "Passionate Lover Red". The Whistle only comes in one standard color.
GPS Tracker Does not have a GPS tracker. Does have a GPS tracker, which is useful for always keeping tabs on your dog.
Mobile Compatibility The FitBark is compatible with both iOS and Android devices. iOS devices must be running iOS 8 or above, and Android devices must be running Android 5 or above. All devices must have Bluetooth. The Whistle is compatible with both iOS and Android devices. IOS devices must be running iOS 9 or above, and Android devices must be running Android 5 or above. All devices must have Bluetooth.
Price A brand-new FitBark is a one time payment for $69.95 online. The Whistle does have a subscription plan. The Whistle 3 is $79.95, and the subscriptions range from $6.95 - 9.95 per month. A subscription plan is required to use the GPS tracking feature.
Battery life/charging FitBark claims its battery life is 10-14 days. Charging the FitBark takes about 1.5 hours. Whistle claims that its battery life lasts up to seven days. Charging the Whistle takes about 2 hours.
Tracking method FitBark tracks your pet's activity through BarkPoints. Calories and sleep scores are also shown. Whistle tracks your pet's activity through intensity and minutes of activity.
Waterproof The FitBark is waterproof (Waterproof specification is IPX7). The Whistle is waterproof (Waterproof specification is IPX7).