I recently acquired a watch with a PreciDrive/HeavyDrive movement. I know the marketing spiel for HeavyDrive: allows for more mass/unbalance in hands, and avoids problems from shocks by applying counterforce with the motor. It's this second bit that fascinates me: does anyone have an idea how it actually works? The first thing that pops to mind is accelerometers but (and I'm not an engineer) it seems to me there's no way you could monitor them within the power budget of a watch that runs for...

How does ETA HeavyDrive REALLY work?