At first these limited applications (checking house prices, for example) were just there to lay the ground work in demonstrating the possibilities of Augmented Reality, but with the full embrace of the internet users themselves will start adding tagged information and geo databases will start opening their doors. Like Wikipedia, Layar should then be able to expand organically until info on every shop, public service and geographical location can be accessed via an API.

So if you find yourself lost and hungry in a strange town just pivot your camera until a McDonalds tag appears and tells you where to head. Or if you see an interesting building and want to know its history, you can pull up the details on your phone right there on the spot.

Layar aims to branch out soon on the Apple iPhone 3GS, essentially putting their API in the hands of a mass market for the first time. They've already released their Layar Reality Browser 2.0 on other phones, which offers new local layers and global content from Flickr, Wikipedia, Google, Yellow Pages and more. The thing is, Wikitude has much the same ideas and is also soon to be made available on the iPhone.

The beauty of AR on a phone is that it can make almost anything appear anywhere

Whilst Layar is essentially an all-in-one application, Wikitude is made of three separate branches. Firstly, the Wikitude World Browser works like Layar to overlay interesting data on your screen that tells you about your surroundings. Next in the line-up is Wikitude.me, a community of mobile augmented reality users who can 'embed unique points of interest (POI) and location-specific, hyperlinked media content' to be viewed on the Wikitude World Browser , in other words the same sort of people who would add content to Wikipedia pages.

Finally, the Wikitude API feature allows programmers to build their own applications - one programme we saw displayed the flag of a country and in which direction its capitol city lay. Another was designed specifically for Geocaching, an outdoor activity in which the participants use a GPS to play hide and seek with buried waterproof containers. Sort of like 21st Century orienteering, Geocaching is played in over 100 countries and to date there are 903,197 caches to be found containing anything from toys to notebooks, so get hunting!