Best of all, it's fully integrated with GCA caches, i.e. if you drop one into a GCA cache and use the GA Code in the Waypoint box, it should find the cache. If the cache can't be found you can list the co-ordinates and include the GA Code in the notes.
Android geocaching app c:geo supports GeoKrety logging.
GeoKrets in Australia
View a list of the GeoKrets in Australia here and a map with currently active GeoKrets shown here. You'll note that it's not big list nor are there many currently active (only 7!), but just like GCA, the more you use it the better it will get.