More on Mobile GPS
Due to a confluence of factors, including continuing miniaturization and falling cost, GPS technology is now everywhere, turning up turning up in a host of electronic devices aimed at the general consumer market, notably - you guessed it - smartphones and PDAs.

How does GPS, which is short for global positioning system, work? Here's the short course: A GPS receiver gathers pulsed signals from as many of the two dozen or so GPS satellites orbiting the earth as it can lock in. Using triangulation -by measuring and comparing the travel time of individual signals - the receiver calculates its position, and it's accurate to within twenty yards or so.

The seeds of the mobile location-based services market were initially sown in the U.S. back in 1996 when the Federal Communications Commission (FCC) began mandating improved e911 service for mobile phone users. If mobile users dial 911, the federal regulators said, the cellular operator must be able to relay accurate information about the caller's location to the Public Safety Answering Point (PSAP) where the call is received.

The SmartPhoneToday staff contributed to this story.