Fitbit today introduced its Charge 4 fitness tracker, and while the design of the new model isn't a huge change from previous versions, there are some new features inside.

The Charge 4 is the first Fitbit tracker with built-in GPS, meaning you no longer need to bring your phone during outdoor workouts to get accurate tracking. The built-in GPS enables the Fitbit Charge 4 to track pace and distance in real-time plus get a heat map synced to your Fitbit app that'll show your workout intensity along your route.

Another new feature of the Fitbit Charge 4 is called Active Zone Minutes. Based on your resting heart rate and age, you'll get personalized heart rate zones to track your effort for any activity and get real-time alerts when you change zones to know if you need to work harder or scale back to be more efficient. You'll get credit for these Active Zone Minutes that'll help you reach the American Heart Association's recommended 150 minutes of moderate activity or 75 minutes of vigorous activity each week.

In addition to all that workout tracking, the Fitbit Charge 4 can track your sleep, too. Sleep Score will give you a daily look at the quality of your sleep, and Smart Wake uses machine learning to determine the optimal time to wake you up. And with an Sp02 sensor, the Charge 4 can see an estimate of the oxygen level variability in your bloodstream, which could indicate variations in your breathing during sleep.

Fitbit has equipped the Charge 4 with Spotify controls, letting you play, pause, and skip music from your wrist. Fitbit Pay is included, too, letting you make payments with nearly 500 issues at retailers in 44 countries and 10 transit systems, including New York's MTA.

The Fitbit Charge 4 is now available for pre-order at a price of $149.95. It'll ship by April 13th.

Fitbit is also selling the Charge 4 SE, which features identical hardware to the regular Charge 4 but comes with an extra reflective band that could be useful during night workouts. The Charge 4 SE is priced at $169.95 and is available for pre-order, with shipments expected by June.

Overall the Fitbit Charge 4 looks like a big upgrade over the Charge 3. That's largely thanks to the built-in GPS, which can really lighten your load during outdoor activity since you'll no longer need to bring your phone along for its GPS. The inclusion of Fitbit Pay support in the regular model Charge 4 is nice, too, because with the Charge 3 it was a feature you had to pay more to get with the SE model.