Interesting question. I know GPS works in the Caribbean of course - most boats have some kind of GPS. My brother in law ran some GPS thing on his laptop in St. Thomas a couple of years ago and it spotted us within 75 yards - even drew on map on his laptop of what is basically our drive way, that isn't even on any print maps I have ever seen. As long as this "off-board navigation software" works on your phone, I don't see why the GPS system wouldn't work.
Anthony for Caribbean-On-Line