Building a location aware Windows Phone 7 application
The Windows Phone 7 SDK contains a couple of APIs for interacting with different parts of the phone hardware, like accessing the camera or initiating a phone call. One of the cool APIs of Windows Phone 7 is the Location API. Just as in the desktop version of .NET Framework 4.0, the Location API enables you to get the approximate location of the user. To find the location of the user, the API uses GPS, WiFi or cell tower triangulation, where the first is the most and the latter least accurate.