Another thing we noticed during the initial teardown is the irregularly-shaped blob of metallic material at the center of the S1.

In all likelihood, this is a heat sink for the S1's tightly packaged processor.

Under the X-ray, this area lines up nicely with the centering magnet for the charger. Possibly Apple designed the magnet to serve a dual purpose—aligning the charger, and bleeding heat from the S1 SiP.