Despite the fact that Fitbit sells more than half a dozen different activity trackers and just started shipping two new ones this spring, its best-selling wearable to date has been the Charge HR, announced back in 2014. The not-too-chunky, not-too-tiny wristband, with its small strip of a display and optical heart rate sensors, seemed to hit the sweet spot for a lot of consumers.

The question now is whether its successor will have the same mass appeal. Fitbit today unveiled the new Charge 2 activity tracker, the successor to the popular Charge HR. The announcement wasn't a huge surprise — the product names had been leaked before, and Fitbit CEO James Park said on a recent earnings call that more devices would be released before the end of the year — but it's surprising to see what Fitbit focused on in this product update.

First off, the display on the Charge 2 is much larger — four times larger, to be exact. It's still not touch-sensitive, though. You press a single physical button to cycle through all of the top-level menu options (steps, heart rate, a whole variety of exercise options, stopwatch, and "Relax") and then you have to tap on the display to go through sub-menus. The difference is that there are sub-menus, something that the Charge HR didn't offer; based on my very brief experience with the Charge 2 so far, the added screen real estate is a nice addition.

The Charge 2 has "connected GPS," something the Charge HR also didn't have. This means that if you have your phone in tow while you're doing some sort of activity that involves location tracking, like running or cycling, the Charge 2 can add GPS tracking to your workout for more accurate distances. Your workout will also appear as a mapped exercise in the Fitbit app after the fact.

The irony escapes no one that we're now supposed to use gadgets to achieve mindfulness

Fitbit is also introducing a metric called Cardio Fitness with the Charge 2. This isn't VO2 max (a measure of maximal oxygen uptake that serious athletes get into) but more like an estimation of it: the Charge 2 will use information like your age, gender, and weight, along with your heart rate levels and your running speed during exercise, to assign you a cardio "score."

Finally, there's a breathing feature on the wristband, called Relax, that guides you through a short 2- or 5-minute breathing exercise. It's not unlike the Breathe feature added to Apple Watch with the watchOS 3 software; the irony escapes no one that we're now supposed to rely on wearable technology, buzzing and nudging and pinging us all day long on our wrists, to achieve some sort of mindfulness.

The Charge 2 costs $149, the same price as the Charge HR. Preorders start today, and Fitbit says it should ship by mid-September. Its expected battery life is around five days.

The addition of connected GPS, along with cardio fitness readings and the Relax feature, are really the key differentiators with this Fitbit. The Surge has built-in GPS, but it's chunky and expensive; the Blaze also has connected GPS through the phone, but it's a watch form factor. With the Charge 2, Fitbit is offering something smaller and less expensive than those two, with connected GPS; the bracelet-style Alta costs slightly less and is arguably more stylish, but doesn't have that GPS option.

One thing worth noting is that the heart rate sensors in the Charge 2 are the same exact sensors found in Fitbit's other products (the company calls this its proprietary "PurePulse" technology). While optical heart rate sensing works okay enough in stable environments, Fitbit has been hit with a class action lawsuit over what some consumers said was inaccurate heart-rate tracking, especially during intense exercise.

In addition to the Charge 2, Fitbit also announced the Flex 2 today, a slimmer, waterproof version of its original Flex tracker. The Fitbit Alta is getting all kinds of fancy, with a new gold-plated version launching for $149.95, and more designer options from designers like Public School and Vera Wang. The Fitbit Blaze has been updated on the software side to include "move reminders" and to show notifications from third-party apps like Gmail, Slack, Facebook, Instagram, and Snapchat.

And Fitbit is clearly making an effort to get people more engaged with its software with the launch of an "Adventures" feature in the Fitbit mobile app, which creates personal challenges for people to participate in (right now it's limited to a few trails in Yosemite National Park and the upcoming New York City Marathon).

Fitbit is still the undisputed leader in the wearables market, claiming nearly 80 percent of the market in the US and around a quarter of the global market for wearables. By ramping up its product releases for the year and putting even more Fitbits on store shelves and in people's faces, the company is clearly hoping to maintain that lead — especially with much larger tech competitors rumored to be putting out their own new wearables this year.

Update: A previous version of this article referred to a new software feature as "Challenges." It's actually called "Adventures," and the trails are found within the Challenges section of the Fitbit mobile app.