Glad you think you might have an ID, I was just taking a wild stab. Although I must say it looks like most pics of the S. bidens (red claw mangrove crabs) have a much different color than yours. Yours is more of a solid red with orange legs in your pics whereas the google search shows a purple face and legs on most S. bidens and those google crabs look like they are maybe smaller than yours. This is what I find googling Sesarma bidens: http://www.google.com/images?q=sesar...iw=950&bih=502 But then yours could be pre-molt and could look different in a few days after shedding and coloring up again.
Post some pics at Panzerwelten if you haven't already and see what the volks there think it might be. I'm sure Oliver will be interested.
I actually got my Geosesarma sp. "Red" Vampire Crabs from Philippe De Vosjoli a reptile book author/breeder. He imported a batch from Sulawesi and I was able to get some of 'em (5 pairs). He breeds the G. bicolor (purple & yellow vampire crabs) but the reds were a new discovery last spring (first import was to Germany in Feb. then here in April or so), they still are only ID'd by "Red" - how exciting a name is that!? LOL
I keep mine on a mixture of peat, bark, crushed oak leaf, sphagnum and live mosses. The Geosesarma eat the substrate they live on as well as meats so they eat the peat and the mosses, not enough to eat it all and they don't bother live plants any. They love to tunnel/burrow through the substrate and make "houses" under plants so, unfortunately this means I rarely ever see them! LOL
I put crushed sea shells and pieces of plaster of paris in their ponds so the water has a bit of buffered hardness, Geosesarma are true FW land crabs dwelling on muddy banks, mossy trees and inside N. ampullarias, never ever needing/wanting salt in their water and giving birth to live young with no free swimming planktonic stage, one day the female has eggs the next there are wingless fruit fly sized crabs darting about.