Something the wise one here notices with the FitBit as well.
It could just as well be counting the number of times you pick up the cups for a sip and the total number of biscuits you dunk and eat. There is no calibration for the kiloJoules from the latter.
Hanging out the washing also scores highly.
Should Apple offer a line in footware?
Built in pedometer, integrated Bluetooth, piezoelectric pressure driven recharging as you walk and work. At least the steps count might be reliable. Apple may likely offer a device to footware manufacturers who pay a license fee to provide a patented moulded pocket in the heel of their products. Altimeter extra for those needing to boast airtime. Dreaming?