Amazfit, makers of such smartwatches as the Bip 5 and the new Balance 2, just released its new Helio Strap 
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Forget the subscription: this fitness band has everything I need to track my progress
The app also has its share of unique metrics intended to provide deeper insights into health behavior. For example, the BioCharge feature generates a number for you in the morning (a score out of 100) that tells you what kind of shape you’re in for the coming day, with the score changing as you progress through the day.
This number is generated from the quality of sleep you got, what kind of day you had yesterday, your resting heart rate, your activity level, and your stress. For example, if you had a stressful day previously and didn’t sleep well, your BioCharge will start out low, putting you at 60 at the start of the day. A great night of rest, however, and you might start the day out at 100.
The app mentions that it needs at least seven days of data to project an accurate assessment, and I found this to be more or less accurate, not just with BioCharge but also with sleep data and PAI, Zepp’s other proprietary health score.
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PAI, or “personal activity indicator,” awards you points every day based on your cardiorespiratory measurements. The intent is to get a weekly score of 100 or greater. This can be hard to do, as the better shape you’re in, the fewer points your workouts generate, pushing you to work harder.
The algorithm here is successful not in that it gives you absolutely perfect data, but because it’s so good at pushing you with just the right amount of what’s realistically achievable. If you’re someone who just needs a nudge to keep your fitness in check, this metric alone is a good way to keep tabs on your activity level for the week.