In my quest to find the best activity trackers for fitness, tradeoffs between features, price, comfort, and style abound. The Jawbone UP24 ($149.99) is no exception. Its sophisticated sleep features are a draw, but it doesn't have a real display showing the time, distance traveled, and so forth. While comfortable and sleek, you have to wear the Jawbone UP24 visibly on your wrist, whereas clip-on devices, such as the Editors' Choice Fitbit One and Withings Pulse, both of which can hide discreetly in a pocket or slip onto the front of a bra. Or take the Basis Carbon Steel Edition, which is more expensive at $199, but masquerades as a wristwatch, while adding a heart rate monitor that reads your heart rate through your skin, a feature that continues to wow me.

Jawbone UP24, an updated version of the original Jawbone UP activity tracker, counts how many steps you take each day, how much exercise you get, and includes some wonderful features for monitoring sleep and waking you at the appropriate time in your sleep cycle. The addition of Bluetooth 4.0 (BLE) syncing is a welcome improvement over the original Jawbone UP, which only uploads data when plugged into the headphone jack of a supported smartphone.

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In terms of price, the Jawbone UP24 is on par with the Nike+ FuelBand SE. I think they're both just a touch expensive, considering other competitors. But between them, the UP24 is the better product, a pliable and comfortable wristband that provides relevant and comprehensible information about you and your daily activity.

Design
Similar to the original Jawbone UP, the hypoallergenic TPU rubber wristband isn't a closed circle. You stretch the two ends of the band open to slide it on and off. Once the Jawbone UP24 is on, the two ends never really sit flat, which isn't problematic, but is a little ugly.

The Jawbone UP24 comes in onyx and persimmon, and it's available in small, medium, and large. 

Charging. One major difference in the Jawbone UP24 from the original is the charging point. In the old band, one of the arms ended in a port that fit into a headphone jack, which is how you charged and synced the device. The new charging point looks the same but is not compatible with a headphone jack. Instead, it fits into a proprietary USB connector, which you can plug into your computer or a wall outlet (you'll need a USB power adapter, which anyone with a smartphone should have). That's how you charge the band.

Syncing. Syncing, however, happens via Bluetooth 4.0 BLE with a smartphone. Both Android and iOS are supported. More specifically: iOS devices newer than iPhone 4S, the fifth-generation iPod touch, the third generation iPad, the iPad mini, and any device running Android 4.3 and later. More on the app in a moment.

Battery. You'll never see the battery, but it's a lithium-ion polymer battery whose charge lasts around five to seven days, depending on use. Setting a lot of vibration alarms, for example, will tax the battery more heavily.

Water-resistant. The Jawbone UP24 is "splash-resistant," but not fully waterproof. Don't swim with it. If you want a fitness tracker for swimming, get the Misfit Shine ($129) ; I like it a lot, but the interface takes some getting used to. If you're a competitive swimmer, or a triathlete, don't get an activity tracker at all, but rather opt for a specialty GPS watch, such as the TomTom Multi-Sport ($199). Sports watches are not pedometers, but for athletes, they're a much better buy.

Jawbone UP Mobile App
Whether you're rocking a classic UP or the new 24, the mobile app is the same. It does have some great features, and where it falls short, like in calorie counting, it connects to other apps and services that do a better job.

The iOS or Android app is your one and only dashboard, because there's no desktop or Web app, which I lament. I spend a lot of time in front of a computer and appreciate the ability to hop online and tinker with my tracker's settings or check my activity status.