If you need to track the whereabouts of your co-workers, or to give them your precise location, try using the free GPS tracking service by InstaMapper. (You still need to pay for mobile data charges though.)
You can install the free InstaMapper client software on your iPhone, Android and BlackBerry (some models only) mobile devices. When you run the InstaMapper client on your phone, it sends your GPS location periodically to InstaMapper's server via 3G or Wi-Fi. Your co-workers will be able to log in to InstaMapper's password-protected Web site and see your present location, as well as your movement trail on Google Map.
On the iPhone, you need to run the InstaMapper client in the foreground; you can't run any other iPhone application while the InstaMapper client is active. On Android phones, it's possible to run the InstaMapper client in the background and you may even set the InstaMapper client to start remotely, triggered by an SMS command.
If you're thinking of building a prototype application for location tracking, you can use the application programming interface (API) provided by InstaMapper. The API can provide real-time GPS coordinates of a particular phone for your application.
Remember that InstaMapper is a free service, so there is no guaranteed level of service. It's good for casual use and for simple prototyping.
I tested InstaMapper on my iPhone and I find that it works reasonably well for a free service. It's very useful for ad hoc GPS tracking, especially for getting somebody to locate me easily when I'm lost.