The Sony GPS gizmo records its position against a time base, I'm not sure the exact rate of recording but it is very frequent. In your computer the supplied software then looks at the time your camera says it took the image, (from EXIF info) and corelates the position of that time with the appropriate image. I think it will work with other than Sony cameras.
Edit:
Found the link:
http://www.sonystyle.com/is-bin/INTE...ductSKU=GPSCS1
PS. Hope I am not violating forum rules with the link.