Expanding BBB via USB modules


I see that there are a number of USB boards available which can increase the available GPIOs of the main device. For expamle: http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT245R.pdf) This is important to me as I would like to have devices which are located some distance from the actual board.

Are the additional GPIOs accessible via the same sysfs interface? How does one detect, identify, and map these additional IO options. Is there a guide to accessing the capabilities introduced through the various USB dongles?