You may have heard this morning that foursquare is launching in the UK. And if you haven't, shame on you for not having Pocket-lint open all day. If you don't know what foursquare is on the other hand, then that's a whole lot more forgiveable seeing as the service only started in March this year at the SXSW technology, music and film extravaganza. So, for the majority of us...

What is foursquare?

In a nutshell, it's a location service-based social network-come-game. What it does in effect is to tell you where your friends are and add a little fun to going out in the evening. It's like Google Lattitude meets a little bit of Facebook, a touch of Twitter, a dash of Qype and even a twist of World of Warcraft. And if that's not a cocktail for hopeless addiction, then we're not sure what is.

How does it work?

The whole system is based around what is known as "checking-in". You check-in from bars and restaurants and any kind of nightspot or watering hole, perhaps with a little message about where you are and what you're doing - all very brief - and the system will then register what you're up to. People who you're friends with will then get pinged a message to let them know your whereabouts and activities, and the idea is that they can then join you if they fancy or just be pleased that you're out having a good time. From the other side of things, if you're out on your own somewhere, suddenly mateless in town or stuck at home and bored, you can see where everyone's at and get yourself down to the party. All pretty simple. The other two things you can do are create a to-do-list of places you've always wanted to go and add to a Top 12 list of your recommendations for other people.

And what about the game?

The clever, or clever-er, part is that you get points for checking-in. The idea is that it encourages you to do so, which then gets the system running and propagates the idea and the fun even further. It's all rather new, even for the developers, and much of the system is still evolving but, at the moment, you get a point for checking in, you get five points if it happens to be from a place you've never checked-in from before; a further point if it's the second, third, fourth etc place of the evening; and another still for checking-in multiple nights in a row, you old booze hound, you. You can only get points for checking-in outside of work hours - presumably to prevent potential mass job loss and alcoholism - but you're always eligible for the five discovery points no matter what time of day it is.

Naturally, the points aren't good for anything other than bragging rights but that's currency a-plenty with a leader board on the site with the top users. Also, if you check-in from the same place more times and more regularly than anyone else, then you might find yourself crowned Mayor of that gaff on the site - an honour that many may try to wrestle from you but then, that's part of the fun. You'll probably begin as rivals and end up the next week amassing 50 points together on some all night bender.

You can also earn badges as you check-in which is where the parallel of World of Warcraft and its Achievements system lies. Firstly, there are badges for the number of times you've checked-in to new establishments from Newbie up to Superstar, plus all sorts of random and more cryptic titles to earn. Word has it that this is where the real addiction lies, especially with the team working on and taking suggestions for all sorts of new badges.

The really clever part

That's basically the fun side of foursquare and what you'll appreciate as a user, but while all this is going on, the owners of the service are also gathering some very considerable review and guide data for all the best spots in a whole bunch of major cities all over the world. It's the kind of user-generated content that Qype specialises in but in a much less in-depth way. What foursquare then decides to do with that is up to the business but there's certainly plenty of commercial scope, if only for the desire of new bars and restaurants to get themselves listed or even to have a badge made just for them.

How do I start?

Like all social networks, just head to the foursquare site and sign up with a free and very brief profile which will ask you for your mobile phone number so it can ping you. Then add a photo and find your friends.

Can anyone use it?

Well, yes and no. Firstly, the system has to be city specific, so there are different networks for a number of different locations. If there doesn't happen to be one in your location then, it's not going to work for you. So far you can play in: Amsterdam, Atlanta, Austin, Boston, Chicago, Dallas / Fort Worth, Denver, Detroit, Houston, Las Vegas, Los Angeles, Miami, Minneapolis / St. Paul, New York City, Philadelphia, Phoenix, Portland, San Diego, San Francisco, Seattle, Washington, DC and now London as well. You'll need a mobile phone to check-in from and a decent SMS package on your price plan or, better still, there's an app for Android, iPhone and soon ones for BlackBerry and the Palm Pre too.