The accelerometer is 3-axis and can certainly work as a pedometer. All you need is an app to pull that data up to the Internet. This is an important capability that we made sure was baked in.
We should add a drawing and dimensions to the main page with more exact figures, but for the moment: roughly 38mm top-to-bottom on the front face, 35mm left-to-right on the front face, and around 12mm in depth. The watch lugs add a bit to that near the base, snuggling your wrist, where they attach to the 22mm strap.