By default, new shape files created by CartoMobile are in WGS84 Latitude/Longitude. If you do not see a .prj with the .shp, .shx, and .dbf files, you should assume the data is in that CRS.
For those working with Cartographica, WGS 84 is available in the standard list of CRS (Set Layer's Projection).
For those working with other GIS systems, this is a common projection known as EPSG:4326 or can be defined in proj4 using:
+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
Or you can download and rename the attached .prj file.