What's the best way to use a 4S for map navigation off- and on-line in the bush? I hear I can't do it. Is this true? That I must buy a Garmin and use both. Anyone out there using an iPhone 4S in weird places with no coverage for maps? How about SIM cards? I Googled them and theirs a trillion. Here, people just say get a local one. Last time I was in China I got so ripped off doing that. I'm trying to do my homework. Does anyone have any input on best SIM cards for Thailand, Cambodia, Vietnam, Laos, and China? Do they include both voice and data? Any help appreciated.