The £119/$129 wearable is a direct challenge to the new and is thinner and lighter than its predecessor, and is more stylish thanks to the metallic accents around the display. The new tracker, which succeeds the excellent , also promises a week-long battery life and water resistance, making it safe...

The Garmin Vivosmart 4 is a simple, slimline, swimproof fitness tracker that allows you to monitor activities, count your steps, check your heart rate and track your sleep.

Slimline and swimproof; Heart rate monitor; Range of modes

Screen is pretty small; No GPS

Garmin's vivosmart 3 fitness tracker tried some interesting things, but it didn't follow through so well on all of them. This year, the company not only needed to make up for the vivosmart 3's faults, but also create something to go head to head with the upcoming Fitbit Charge 3 .

Thin; lightweight design OLED display is much better than the vivosmart 3's Accurate fitness tracker overall Advanced sleep metrics are very useful Body Battery is useful for determining how tired/energetic you are Pulse ox sensor is nice to have on a lower-end tracker 5ATM water resistance Garmin...

No phone-to-GPS tethering option Narrow display can be difficult to use Pulse ox sensor is sometimes off; doesn't take readings all night

For the same price, the Fitbit Alta HR has a similar look, feel, and functionality, but with more flexible fashion options thanks to its swappable bands. It also has a more responsive touch screen and a better user interface, but less detailed metrics.

Accurate; Long battery life; Automatic activity tracking; Measures blood oxygen levels, sleep, stress, and body recovery; Slim, sleek design

Touch screen could be more responsive; Uses proprietary charger

Tracking sleep, stress and energy levels is endlessly interesting with the sleek, stylish Vivosmart 4, but an unresponsive display and inaccurate run tracking proved frustrating.

Slim; stylish design; Body Battery feature; Advanced health tools

Inaccurate run tracking; Small; unresponsive screen

This new tracker has the common features (sleep stages, heart rate, stress) and the new Body battery that is very interesting and also pulse ox. I already own the Fenix 5 & Vivosport, I highly recommend it!

The appetite for fitness trackers may be slowly diminishing as smartwatches start to displace them, but for the time being there's plenty of juice for Garmin, Fitbit and others to squeeze out of the market.

Body Battery works well; Pulse ox could be handy for some; Beautiful design

No GPS; Smart notifications messy; Interface is twitchy

A new style, metrics, and sensors in the Vivosmart 4 shows Garmin is willing to keep its fitness trackers fresh and exciting.

Slim; fashionable design; Affordable price; Body battery; Pulse ox

Small display for notifications; No GPS or connected GPS

Fitness tech companies, particularly Fitbit and Garmin, want to monitor the level of oxygen in your blood. It's a metric that could help spot signs of sleep apnea and other breathing-related problems, so companies have been scrambling to perfect their SpO2 sensors and incorporate this data into...

Attractive; lightweight design; Informative Body Battery metric; Great battery life; even with SpO2 sensor on during sleep; On-device music controls; Works with Android and iOS devices; Syncs with Apple Health

Not as many on-device workouts to track; No connected GPS; No NFC for Garmin Pay; Few communication tools (only Android users will get quick replies for messages); No female health tracking features; Cannot switch out bands

I was looking for a device that would be able to monitor my sleep patterns with an added benefit of oxygen levels. What I found with the Vivosmart 4 is an extremely lightweight device that is small and thin enough not to be distracting on the wrist when worn.