On paper Sony's GPS -CS1 is the perfect gadget for the urban photographer/blogger who wants to geotag their photographs for display in either Google Maps or Google Earth.
The attraction of the GPS-CS1 is that it will work with any camera that can record a time and date - ie the majority of digital cameras. The system simply attaches to a bag or belt clip and records your track independently of the camera. Whenever you take a picture the time and date will be the same as the GPS, this allows the supplied software to link the GPS location with the photograph.
By changing the photo's EXIF header to include location the images can then be easily linked to Google Maps or Google Earth via services such as Flickr or Picasa. The unit takes a reading every 15 seconds and battery life lasts 10 hours of continuous use.
On paper then the Sony GPS-CS1 is perfect so why don't we have any examples or Google Maps to demonstrate the output? Basically the unit is close to useless in urban areas - our tests in London only worked if we sat in an open space for a few minutes, as soon as we went to take any photographs the unit lost its signal and stopped tracking.
While GPS coverage in urban areas is a known problem, the Sony unit seems to have a low sensitivity. With only a basic flashing LED to communicate connection it is easy to walk around town tacking photographs only to arrive back at the office to find that you don't have any data.
In short if you live in an urban area then sadly the Sony GPS-CS1 turns out to be an expensive keyring, if your out of town its a great, if expensive, solution to geotagging photographs.