That last part is one of the stranger features: two built-in microphones listen to your voice throughout the day and tell you how you sounded. You might have thought your tone was affectionate but the app could reveal you actually sounded bored. (You can turn off the mics whenever you want, though.)
It's water resistant so you can swim with it and it will automatically track and identify activities such as walking, running, swimming and more.
You can access all this information via the Amazon Halo app, which is split into four sections: Activity, Sleep, Tone and Body.
It doesn’t focus on your weight: it uses your phone camera to take four photos of your body shape (front, back, left, right) which Amazon says is up to twice as accurate as smart scales for assessing body fat percentage, which is says is a better indicator of overall health than weight or BMI alone. It will then track this over time and show a 3D model of your body so you can see the changes for yourself.
Amazon says it deletes the photos after they're uploaded to its servers.
When is the Amazon Halo release date?
It’s currently available on Amazon’s Early Access programme in the US. You have to request to join this: you can’t just order one.
How much does Amazon Halo cost?
Its regular price is $99.99, but has an introductory discount which knocks 35% off, making it only $64.99.
It comes in three colours: Black band with Onyx sensor capsule, Blush with Rose and Winter with Silver. As you’d expect, you can buy additional bands, which are initially available in six colours for $19.99 each ($15.99 for Early Access customers).
To use most of the features you’ll have to subscribe, which costs $3.99 per month (but you get six months free). That gets you access to everything over and above steps, sleep tracking and heart rate.
When you subscribe you unlock the body and tone monitoring, and you get ‘Labs’, many of which are four-week challenges that aim to change your habits for a healthier lifestyle. Amazon says these must be scientific evidence they are effective, too.
Amazon has also partnered with WW (formerly Weight Watchers) and you can link your account so your Halo data is funnelled into WW’s FitPoints system.
There will be various promotions from WW including options to get a free Halo band when you sign up for a WW membership.
Like many new Amazon products, we expect the Halo will be exclusive to the US for a while, possibly longer than usual as it will have to build local partnerships in each country it wants to launch the band in order to persuade buyers to subscribe.