Dark Reading covered a talk at SOURCE on tracking GSM cell phones using a variety of public data, cell tower triangulation, and voicemail hacking techniques.

FORBES: Conference Roundup: Google Smacked, Clicks Jacked, Cisco Wifi Hacked, Cell Phones Tracked

So while the phone may have GSM network access on shore (because no CDMA signal is found), that is not the case when you are on a ship because ships provide both GSM and CDMA cell sites.

FORBES: Verizon Smartphones And Cruise Ships Don't Mix

Americans are at a disadvantage when it comes to cell phones overseas, because most of the world uses a GSM (Global System for Mobile Communications) standard, Schukai said.

CNN: Navigating cell phone headaches overseas

Traditionally, engineers who wanted multilingual phones had to laboriously design custom chips. ("Dual-mode" cell phones that can hop between, say, TDMA and GSM, have been around for years.) Once they are finally designed, such chips can be mass-produced cheaply and consume a reasonable amount of battery juice.

FORBES: Bridging The Gaps