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Ah. Any way to see it in action without owning a Garmin device?
I don't think so. Garmin also doesn't include some data (steps, etc) without one of their smart bands, either.

Garmin data can also be read by Nike+ Run and Under Armour Record, although UA's app sends you to the MapMyFitness app to view details when you tap on the run.

(Under Armour bought MapMyFitness, BTW)
 
Trying an experiment now --

I think I could add a data point for BMR in the Health app under Health Data -> Fitness -> Resting Calories. I adjusted it a hundred calories lower than what was shown in Activity's Move section. We'll see if the new number sticks.
 
Trying an experiment now --

I think I could add a data point for BMR in the Health app under Health Data -> Fitness -> Resting Calories. I adjusted it a hundred calories lower than what was shown in Activity's Move section. We'll see if the new number sticks.
Update:

Nope, it didn't stick. Scrolling back in Activity, I also don't see the adjusted number I added.
 
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