I was thinking of a Vampuire Crab setup myself ,the got them in a petshop around my location.
The guys at the petshop keep 3 of them in an aquarium half-filled with water ,and for the land part ,they use one of those decorative turtle rocks wiyth a circulating pump inside......of course that is just temporary......they should be allowed to burrow(dunno in what exactly) ,from what I read online.Maybe they would be happy with at least some hiding holes.
This is the rock
http://www.ferplast.com/en/shop/dover-3
I found this example of a setup online
http://www.octopusgallery.net/2014/03/31/aquarium-projects-crab-paludarium/ ,although not ideal ,it gives some useful info about their environment.
Most people seem to use 2/3 land ,I heard that paludarium moss is sometimes used ,covered with paludarium leaf litter(don't know the name)
Geosesarma sp -Geo means "land" ,so it must be pretty important for them.I'm not sure if they like to burrow in sand or rather moss/leaf litter.
I found that ,while info on this species is not so rare as it used to be ,accurate info about how to create the best habitat is still a debate.
Good luck with your searching ,keep this thread alive!!