Image source: Fitbit.

Fitbit (FIT) just unveiled the highly anticipated Charge 2 and Flex 2. Investors have eagerly awaited details on the updated fitness trackers that will be a major determinant of the company's sales growth -- or lack thereof -- in the second half of the year. Even though Fitbit's top-line grew 48% year-over-year in the past quarter, sales have been decelerating and the stock is down 50% year-to-date due to concerns over slowing sales and lower profit margins.

It seems Fitbit delivered on expectations that the two new devices seem to have what it takes to accelerate sales, as the stock climbed higher following the announcement on Aug. 29, though the stock has since pulled back. The two fitness trackers have enough new features that they should attract new customers, encourage old customers to upgrade, and boost sales in the back half of the year.

Let's take a closer look.

New features

The Fitbit Charge 2 provides several significant upgrades to the company's best-selling device. Most noticeable is the screen -- four times the size of the original Charge's. The most important addition is multisport mode, allowing users to track activities beyond running, such as weightlifting, cycling, and yoga. Other new features include personalized cardio fitness monitoring, a guided breathing relaxation mode, and a sleeker design. The Charge 2 is priced at $149.95.   

The Fitbit Flex 2 is 30% smaller than its predecessor and Fitbit's first swim-proof device, water-resistant up to 50 meters. Flex 2 still uses the same five-LED light tracking system, but the tracker can now be removed and placed into other bands and fashionable accessories such as bangles and pendants. Another new feature is call and text notification when Bluetooth-connected to a smartphone. The Flex 2 is priced at $99.95   

Stacking up against the competition

Fitbit can't rest on its laurels as the leading fitness-tracking device manufacturer and needs to continue launching new models such as the Flex 2 and Charge 2. Competition among wearables companies has heated up over the past several years, as companies such as Garmin (GRMN 1.94%) and Apple (AAPL -0.66%) have launched more advanced products with a greater number of features.

Garmin has an extensive product mix of smartwatches, fitness bands, and other activity trackers. Garmin has also offered fitness-tracking devices for a while that include newly added Fitbit features such as multisport mode and the ability to track swimming workouts. Fitbit's a little late with the addition of its first swim-proof tracking device, but with prices for the Flex 2 starting at $99, it'll be an attractive option for customers who don't want to spend $219 and up on Garmin's devices that are capable of tracking swimming workouts.  

Even though Apple doesn't sell a fitness band, it's still a major competitor for Fitbit. The Health app on its newer smartphones offers basic health monitoring, and there is no shortage of free activity-tracking apps available in the iTunes store. At Apple's Sept. 7 event it released the Watch Series 2 with additional features that could steal customers from Fitbit. While there is a sizable price gap between the Apple Watch Series 2's starting price of $370 and Fitbit's devices, the Apple Watch is now swim-proof and has built-in GPS allowing users to track workouts without needing to bring their smartphone along. Apple also partnered with Nike to launch the Apple Watch Nike+ incorporating the Nike+ app and other features into the watch to provide a dedicated device for runners.

Fitbit learned from the popularity of Apple's Watch accessories and is offering interchangeable bands in a variety of materials for the Flex 2 and Charge 2. The Flex 2's activity tracker can also be removed from the device and placed into its new Luxe Collection of fashionable silver and gold-plated bangles and pendants. The accessories could increase sales and boost profits if the margins are higher than its devices.  

Attracting new and old customers

Fitbit's new devices could attract a sizable amount of new customers and spur existing Fitbit owners to upgrade their old devices. The addition of multisport mode on the Charge 2 and the swim-proof Flex 2 could spur members of the fitness community who swim, lift weights, and cycle to consider purchasing a Fitbit. These new features also provide substantial upgrades to older models, which could encourage current Fitbit owners to upgrade their devices. It's too soon to tell, but these new fitness trackers could be what gets Fitbit stock moving back toward its $20 IPO price.