Augmented Reality (AR) is the term for technology that presents the user with a 'mixed' view of the physical world combining a video image of a location together with an overlaid computer-generated view providing information about that location.

A simple example would be the practice of artificially defining pitch lines during sports television broadcasts to enable the viewer to better appreciate team territory possession or possible penalty offences.

A number of manufacturers have developed applications for their handsets harnessing this technology: Google have released an application called Goggles for the Android platform that enables the user to focus on a geographical landmark using their PDA's built-in camera, upload that image to Google, and have information about that building / natural feature returned (provided that Google's image-recognition technology can determine what it is you're looking at). The service can also be used by taking pictures of book covers, albums, you name it:

And if you don't believe the video, here it is in action:

There are other very impressive applications available that provide similar functionality. Wikitude (http://www.wikitude.org/) can overlay real-time facts about a given location on your device's screen when that location is focused on via the device's built-in camera:

The application also integrates with Google Maps and can be used in GPS mode to show you items of interest based on your location. When I used the application on the HTC Tattoo it automatically told me about the Bournemouth International Centre sat right on my doorstep...as well as my nearest Tesco superstore:

TAT Augmented ID (http://www.tat.se) is a similar application but not for geographical locations or natural features, this application is for people: call up a picture of an individual and using face-recognition technology that's person's Facebook profile will be overlaid across that photo on your device's screen:

Nearest Tube (http://www.acrossair.com/apps_nearesttube.htm) is an application for the iPhone that allows you to focus on a location in London and have your nearest Tube station (that's the London Underground for non UK-residents!) displayed on-screen together with distance and direction information. A version is also available for New York.

Layar (http://layar.com) is an augmented reality application for the Android platform that allows developers to create overlaid content for specific locations, be it a 3D reconstruction of the Colosseum in Rome or the Beatles' Liverpool.

Layar's applications can be listed by most popular, or by relevance to your location. Using your device's built-in GPS capability you can take advantage of such applications as 'find my nearest pub':

TwittARound is an application for the iPhone that allows you to focus on a location using the camera and have people's tweets overlaid across the image, together with information about who tweeted...and from how far away:

Applications are also available for sporting events such as Wimbledon to assist members of the public find the correct court for the match they want to view as well as locate bars, restaurants and rest facilities.

The future is now, and it's bigger than the real thing!