I wonder how much power running the accelerometer uses? It isn't free to keep track of that. Back on my Note (1) Samsung had a bunch of gestures related to the accelerometer, and leaving them enabled drained a significant amount of battery.
Probably will be the same thing as pedometers in newer mobile SOCs, that don't use significant power. Snapdragon S800 (Nexus 5) and up.
It depends on how many updates a second. One update a second is about 10µA, with a higher frequency costing more.
Also the bi directional charging with type C is super cool.