Jawbone unveils the Up3, its most sophisticated health band yet

Nope, Jawbone still doesn't have a smartwatch of its own. But with the $180 (£150) Up3, its latest health-tracking wristband, the company is making a clear case for why it doesn't need a smartwatch (yet). With sensor technology from last year's BodyMedia purchase, Jawbone has crafted an all-day activity tracker that appears more refined than most of its competitors. Slimmer than Microsoft's recently announced Band and the Up24 , its sensors go deeper than Jawbone has ever gone before. Perhaps most significantly, it features heart rate monitoring that may actually work consistently, unlike what we've seen from many competitors. In short, the Up3 is a health tracker built for people obsessed with health tracking. If you're looking for something a bit more entry-level, consider the new Up Move, which the company also announced today.

Naturally, the Up3 features all of the usual activity and sleep tracking features from the Up24. But thanks to a whole bunch of new gear -- including a tri-axis accelerometer, bioimpedance sensor, skin sensors and ambient temperature sensor -- it also goes much further. The Up3 can automatically detect new activities -- for example, if you went for a bike ride -- without any prompting, and its sleep tracking can now give you a detailed look at your light, deep and REM sleep.

As with all of Jawbone's health trackers, the company once again tapped Yves Béhar, its chief creative officer and a renowned industrial designer, to craft the Up3. It's a considerable upgrade over the past two Up bands -- and that's a big deal, since they're among my favorite wearable designs so far. Rather than a single, continuous bracelet design, the Up3 features a central housing for most of its gadgetry surrounded by two extremely flexible arms. The design is thinner and doesn't stand out as much as past Up models, making it ideal for wearing alongside other arm accessories.

Best of all, the Up3's new design makes it a one-size-fits-all device. Previously, you had to choose between small-, medium- or large-sized Up models. Jawbone developed a new type of clasp for the Up3 -- which, honestly, resembles a fancy bra clasp -- to make it easily adjustable for all sorts of body types. It's a big step up from awkward and clunky clasps I've seen from other companies (hello, Fitbit and Samsung).

The Up3 still doesn't feature any sort of screen -- you'll still be looking at blinking LEDs -- but its central unit is now touch sensitive, so you won't have to go fishing for any buttons. Jawbone says it will get around seven days' worth of battery life, and it's also water-resistant up to 10 meters.

The Up3's combination of design and functionality is best shown by how it handles heart rate monitoring. Most other wearables on the market rely on green LED sensors that have to be held close to the skin very carefully to detect your heart rate. The Up3, on the other hand, gets your heart rate by measuring galvanic skin response using the skin and temperature sensors in its armbands. At launch, the Up3 will be able to measure your heart rate when you're at rest, but an update will eventually enable on-demand heart rate monitoring.

When it comes to wearables, we've seen plenty of sensor-laden devices that would be tough to wear all day, and plenty of pretty-yet-functionally-light gadgets that may not be robust enough for health-tracking addicts. With its slick design and bevy of sensors, the Up3 could finally end up being the unicorn device to bridge that gap. (Though I'm sad there's still no independent GPS functionality.)

And what of the Jawbone smartwatch? The company has opened up its platform to competing health platforms, including Apple's HealthKit, and it has apps available on Android Wear and Pebble watches. With such widespread support across the disparate smartwatch market, it actually makes more sense for Jawbone to avoid releasing its own smartwatch.

"The good smartwatches have become good platforms, and we've taken full advantage of that," Andrew Rosenthal, Jawbone's group manager for wellness and platforms, told us in an interview. "We believe in platforms -- we're going to show up where the smartwatch is, where people want to put a big display on their wrist, but not everybody wants to do that."

The black version of the Up3 will be available for $180 (£150) by the end of the year, with additional colors coming next year. (Judging from the mockups I've seen, it may be worth waiting for the more colorful variants.)