In my N1, it is cell- and WiFi-assisted, but that doesn't mean that it doesn't work outside those areas. It just means that it performs initial acquisition more quickly, as it has other ways to get general location and GMT. I would assume the same is true for the iPhone. Now, if you have no data coverage, I wouldn't be surprised if the navigation apps fail to work. I don't think that either device has mapping data built into it.