GraphHopper is an
open source
routing engine with commercial nature for some more advanced
features.
In order to use it with Cruiser you will need a 'graph' for the
area you want.
A 'graph' is essentially a folder with specific routing files
inside.
Once you have this folder in your device you have to select it
(via long press) at Settings - Routing in Cruiser.
To
create
routing graphs for an area you can use
Atlas
a Java map / navigation application (equivalent of Cruiser).
To do that, download a region from
Geofabrik and in Atlas
use the Routing - 'Create graph' menu.
First it'll ask for the input osm/pbf file and then for the output
folder to put the graph in.