One great deal we’ve found today is on the immensely useful Fitbit Charge 6 fitness tracker. This handy device can be a huge boon for your health, and while it’d normally set you back $160, this Prime Day deal knocks it down by 38% to just $100.

From telling you how fast you are “ageing”, to giving you a sleep score and even keeping tabs on your blood pressure — fitness trackers and smart watches are more focused on health than ever.

Fitness trackers often fail people with obesity by underestimating their energy burn, leading to discouraging results and misguided health data. A scientist's frustrating experience in an exercise class with his mother-in-law where her effort wasn t reflected on the fitness leaderboard sparked a breakthrough.

You get just about every possible health metric from the Whoop MG, but it's auto-detection lets it down. How does it fare overall?