Technically, acceleration is movement in an inertial system... Anyway, I was wondering for a long time, why phones/watched don't attempt to do it (at least, I never saw useful results of it). Surely it would be more useful to me than nothing, when lost in a labyrinth underground. I always assumed, that results are so horrible (close to random) that nobody even bothers. But then it doesn't tell me much if there is an accelerometer 1000 or 1M times more accurate, in a shoe-box or otherwise. Like, how often does it have to re-calibrate after all?

Are there any records of how currently available consumer devices measure up in this regard?