The FitBit Flex is the most recent entry in the expanding line-up of personal data trackers - also known as fitness wristbands, motivational gadgets, or that thing the annoying over-achiever wears at the gym.

Designed to help you monitor some or all of your daily exercise, calorie expenditure, sleep quality and diet, these bands and doodads are becoming increasingly popular, cheap and mainstream.

At just £79.99, in a well-designed and unobtrusive package and with a genuinely useful range of sensors and services, the Fitbit Flex has some clear advantages over the competition. Unfortunately it also has some shortcomings that mean while it's a serious contender in the market, it's not the obvious champion.

SEE ALSO: Jawbone UP Review | Nike FuelBand Review


In terms of build quality, the Fitbit Flex is a mixed bag. Where the Jawbone Up and Nike FuelBand are single-piece devices, the Flex is actually a small sensor which fits into a rubberised band, but has to be removed to charge. The benefit is that you can swap bands with those of different colours, and, crucially, sizes (two are included). The bottom of the band is thin and doesn't catch on clothing like the Jawbone, and it's not as bulky as Nike's offering. While it's not easy to clip with one hand, the Flex is secure and strong. It's also waterproof - even when swimming, again a benefit over other bands - and very light.

The downside is that, in this form factor, the Flex is fiddly, and the actual sensor itself is a bit bulky, making the band feel more conspicuous than its competitors. It also loses a few of the features of other Fitbit devices, such as the clip-on Fitbit One which also includes altitude tracking.

The Flex does have a limited display, which shows a row of five white LEDs. Each of these lights up when you hit 20% of your daily movement goal. You tap the device twice to wake it up, and three more to set it to sleep tracking mode. It's very simple and it's nice to monitor your progress without resorting to the app.

Functionally the Flex is very solid. Sleep tracking and step counting worked fine, though it did seem to register a few more steps per day compared to the Jawbone Up. We liked the unobtrusive vibration alarms when you hit your daily Active Minutes goal, and the sleep alarm also worked as expected.


Another advantage over the Up and the FuelBand is the inclusion of Bluetooth 4.0 and NFC, which makes the band easy to connect to your device (with little power drain) and constantly update the stats both on your phone and online. Being able to track your progress constantly is a real boost, and the high quality apps for iOS, Android, Windows Phone 8 and the web are universally excellent, with a clear and useful range of visualisers, graphs and export-import options.

Unfortunately there are also a number of niggles. Battery life is about five days - half that of the Up, even less compared to the Fuelband. The range of apps that plug into the Fitbit ecosystem isn't as extensive as Jawbone's new API ecosystem, and the device itself isn't as simple or easy as the FuelBand. And the design - while almost invisible - is a bit dull. Which when you're wearing it every day is a shame.

It's also disappointing that gaining real insights from your data - how you can fit in more exercise, what foods would help you improve, when you get the best sleep and why - isn't easy with the Flex. Without care and experimentation with how to make sense of that information, you can be left resorting to using it as a simple pedometer - and that's probably not worth the money.

Overall however the Flex is definitely a solid, simple choice if you want to get into the personal data game. It's flaws aren't fundamental, and if you're prepared to commit to using it you'll get a lot out of the product. But if you've tried a few of these gadgets before, the Flex is a bit of a let down. Like its competitors, it shows hints of what's possible but doesn't get the elusive cocktail quite right on its own.


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  • Jawbone Up

    While it's rather more fiddly than the Nike Fuelband, the UP gives you more control over your data, is a lighter and arguably more attractive device to wear on your wrist and is complemented by 10-day battery and an excellent app which links into several external services to share data on iOS. <a href="" target="_blank">It's not infallible, but it's an good option if you want to track your activity easily and effectively</a>.

  • Fitbit One Review

    The Fitbit One clips to your clothes to measure the steps you take, stairs you climb, and the quality of your sleep. We prefer it to the wristband version, which lacks altitude tracking.

  • Nike Fuelband SE

    The Nike Fuelband is one of the most attractive and intuitive fitness trackers on the market - and the new SE edition is the best one yet, adding Bluetooth LE for constant syncing with your iPhone, 'Session' markers and limited sleep tracking. It's not a complex gadget, and it's hurt by the lack of Android compatibility. <a href="" target="_blank">But it works, is stylish and has earned a legion of fans.</a>

  • Bose SIE2i Sports Headphones

    <a href="" target="_blank">For £129.95 you might expect that these Bose headphones</a> would be Bluetooth enabled. Sadly, they're not - but they are totally water resistant, secure in the ear and have fantastic sound quality. They also come with in-line controls and a microphone designed for the iPhone, and a fitness armband to hold your music player safe when you work out.

  • iPod Nano 7th Generation

    Apple's latest music player is small, thin, light, has a two-inch screen and is Bluetooth enabled. For our money it's still the best all-around music player if you're mainly using it for exercise - though we do miss the wearability of the 'mini wristwatch' style 6th generation.

  • FINIS SwiMP3 Waterproof Headphones

    <a href="" target="_blank">The FINIS SwiMP3 headphones (£93)</a> are a stunning bit of kit which transmit music through your cheekbones via induction. It's one of the only pair of headphones you can wear in the pool, and if you're spending a lot of time underwater and need an Andrew WK boost on your 50th lap, it might make the difference. (£93)

  • Withings Smart Body Scale

    If you want to get fitter, it's worth knowing the state of play before you start - and during your programme. The <a href="" target="_blank">Withings Smart Body Scale</a> will give you that. It's able to accurately track your weight, body fat and various other stats, and sync them to your phone so you can easily monitor progress over time. They're pricey - but they might make the difference.

  • Adidas Boost

    Many shoe companies boast about the energy-saving, world-changing, etc etc tech of their trainers. The Adidas Boost are the only pair in recent memory that we've been genuinely convinced by. Stunningly 'bouncey' (there's no other way for it), they return more energy to your legs as you run, conserving energy and give you a literal boost to make it that extra mile. Check they're suited for your gait through - they aren't great for those who need a little extra support.

  • GoPro HERO 3

    Alongside being one of the most flexible, durable and tiniest sports cameras on the market, the <a href="" target="_blank">GoPro Hero 3 Black action camera (£349)</a> can record in up to 4K resolution. If you're getting fit on a bike, on skis, in the sea, on a board - or doing anything else which conceivably might be of interest to the outside world - you should get one.