Island will rent a GPS with their cars, it's a Jamaica-specific one. My phone, a Droid, lets me download maps of JA and my GPS will work with them (don't need data for GPS to work on my particular phone). I can't use google maps navigation though, since it requires data. Or I guess I could, if I wanted to pay for data roaming, but I don't.

The JamNav is for Garmin only, unless things have changed recently. That's here: http://www.gpstravelmaps.com/jamaica.php

iPhone has this: http://itunes.apple.com/us/app/jamai...346773439?mt=8