From Sigma:
The Sigma Corporation is pleased to announce the release of the new SIGMA USB DOCK, the accessory dedicated for Contemporary, Art, and Sports product lines that enables you to operate lens firmware update as well as customization including the focus setting.
By connecting the USB cable to a computer, SIGMA USB DOCK enables photographers to update the lens firmware and adjust parameters such as focus. The adjustment is processed with special software (SIGMA Optimization Pro). The AF speed, focus limiter and OS function are also customizable for Sports lenses.