The Unofficial Apple Blog has posted a program for the iPhone which enlists the help of Twitter to alert the user — or someone else — of the global coordinates of a properly-enabled device.
The command-line program obtains the location of the cell tower nearest to the iPhone, in latitude and longitude through Google Maps.
To make this information accessible, the user must give the iPhone its own personal Twitter account. For those unfamiliar, "Twittering" is a moment-by-moment status update similar to the "What are you doing now?" status bar in Facebook.
By automatically connecting to the internet via EDGE or Wi-Fi, and running a Twitter shell script which the user can set to run at varying intervals, the phone’s latitude and longitude are automatically posted on Twitter.
While the program is listed as a "LoJack" solution for the iPhone, which would alert the user of their lost or stolen device, the clandestine nature of the script is conducive to more devious uses. Certainly it is nice to track one’s own property, but there are plenty out there who’d prefer to track others instead.