With a battery life of up to 7 days—and up to 5 hours when using GPS—Fitbit Charge 4 lets you do more with less charging. Varies with use and other factors. Fitbit Pay Do a mild, ten-minute workout mostly in your fat-burning heart-rate zone (zone 3, normally), for example, and you’ll earn ten Active Zone Minutes towards your daily 30-minute target; up the intensity to your cardio and peak heart rate zones (usually defined as zones four and five) and you’ll get double credit for any time spent in those zones. The Fitbit Charge 4 is a real evolution from its predecessor, and GPS is an excellent addition that helps bridge the gap between fitness bands and fully-fledged sports watches. Many other apps fitness provide you with an estimate of spent moving, but these measurements are often connected to footsteps rather than heart rate and are therefore less accurate for indoor activities. Fitbit Premium Fitbit has also brought its Smart Wake feature to the Charge 4; the company says it uses machine learning to know the best time to rouse you from your slumber, a feature my toddler has perfected without the assistance of advanced algorithms. Fitbit Charge 4: Spotify controls

It's also important to note that, although the device can detect when you've started a workout automatically, you won't be able to view a GPS map of the workout unless you selected an activity type before starting. Provided you've done so, you'll be shown your route together with speed, distance and heart rate. It's a lot less data than you'd get from a dedicated running watch, but will be ample for a casual runner. The Fitbit Luxe has a vivid, high resolution AMOLED screen (Image credit: Fitbit) Features Smartwatch features Your goal is to spend 150 minutes in each heart rate zone (fat burn, and cardio and peak combined) during the course of a week. It’s a concept similar to Intensity Minutes in Garmin Connect, and is based on recommendations from the World Health Organization and the NHS.When running, I’d much rather be able to press a button, as manual dexterity isn’t my strongest suit when going at speed. In particular, I found it very easy to accidentally double tap and skip over the screen I wanted, forcing me to cycle through the lot again with. Go into exercise mode during your favourite workouts to set a goal for each workout and see real-time progress of your effort on screen. Built-In GPS

As with the previous model, the Charge 5 comes with built-in GPS and there are some additional sensors this time around, giving the Charge 5 the ability to measure electrodermal activity (EDA) and perform electrocardiogram (ECG) tests. The latter isn’t available at launch, however, with Fitbit set to enable the functionality later this year. Both also have a 'smart wake' alarm, which makes the watch vibrate gently at the optimum point in your sleep cycle, so you wake feeling fresh and without disturbing your partner. The Fitbit Charge 4 has a more angular design than the Fitbit Luxe, with a plastic case rather than stainless steel (Image credit: Fitbit)See which heart rate zone you’re in to gauge if you’re working hard enough to reach your goals. Goal-Based Exercises During workouts, get real-time stats on screen to see whether you’re in Fat Burn, Cardio or Peak zone, so you can dial the effort up or down according to your goals. Workout Intensity Map That all changes with the Versa 3, the first Versa smartwatch to feature built-in GPS. That’s not where the upgrades stop, either. The Versa 3 also comes with an upgraded “multipath” heart-rate sensor, a screen that fills more of the front of the watch body, plus the ability to take phone calls. Though it’s not live in the UK yet, Google Assistant will also be coming to the Versa 3 in a later update. The Charge 5 has lots more health and fitness tools to offer, though – including an EDA (electrodermal activity) sensor, as seen on the Fitbit Sense. This uses your skin's conductivity to assess physiological changes brought about by stress. The Fitbit app then helps you understand the factors that affect your stress levels, and take steps to manage it.