This new algorithm calculates the number of degrees that the wrist has
rolled, and checks if that is above a threshold.
First it checks if the wrist is still enough for the acceleration values
to be considered mostly from gravity. It does this by calculating the
mean over the past 2 SystemTask loops, and checking that the variance
from that mean is below a threshold.
Then it calculates the angle the wrist is being held at, and calculates
the difference from the angle some time ago. If this difference is above
the threshold, it wakes the watch.
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