Sept. 10, 2013, 11:17 p.m.

I think he is on to something.

But the really interesting – and in the long-term important – sensor in the iPhone 5S is the M7, a “motion co-processor” which allows it to measure data from the accelerometer, gyroscope and compass without draining the battery as heavily as would be required if the A7 processor were used. Effectively, using the CoreMotion API, apps can access data about movement all day, without destroying the battery life.

I wonder if everything is sensitive enough that this could be used to do inertial positioning in between infrequent GPS fixes?

Oh, and another thing, this would probably make sense in something smaller than a phone, right?