foursquare is a cross between a friend-finder, a social city-guide and a game that rewards you for doing interesting things.

Yesterday was a good day – it was inadvertently brought to my attention that foursquare is finally available in Perth! And, it comes only a couple of months after its Australian debut in Sydney, Melbourne and Brisbane.

Here’s how it works:
Using a mobile app, mobile web or SMS (US only), users voluntarily check-in at a variety of locations – cafes, stores, bars, parks – and in doing so alert friends of their whereabouts… perfect if they’re in the area and keen to drop in to say hello. It’s also possible to check-in and keep the location private – designed for those times when three’s a crowd.

When checking-in, users can share tips (i.e. try the frites at Little Creatures!) and add activities to personal to-do lists. Check-ins earn points; there are extra points awarded for going to new places and the user who has checked-in most at a given location becomes the “Mayor”. Users can also unlock badges by checking in at interesting places… it’s a competition to explore your city!

Player Please! - a badge that is unlocked by checking-in with 3 members of the opposite sex.

I first became hooked on foursquare while living in NYC and I would rank it amongst my favorite iPhone apps. Why? Because it satisfies every reason I’d ever use an app:

Utility: 1, it enables you to locate people and places, and 2, it offers user recommendations/tips for various locations

Communication: the app obviously facilitates lateral communication and also has Facebook and Twitter integration

Competition: don’t forget that this is also a game – you’re competing to check-in at the most places and unlock badges by doing unusual things (you don’t know how to unlock badges until you’ve unlocked them)

Social networking: the community aspect ties it all together – the tips that pop-up alongside venues are from your friends (*ahem, word-of-mouth from a trusted source), you’re able to catch up with your friends, you’re in competition with your friends.

And then there’s foursquare for Businesses, which gives retailers an opportunity to alert users of promotions when they’re in the area.. imagine checking-in at Starbucks and immediately getting a notification that the Dome just across the road is offering 2 for 1 coffees! In addition to this, many retailers offer special discounts to their establishment’s current Mayor – which effectively rewards the best customers and creates an incentive for other patrons to frequent.

Charities are also seeing benefit in foursquare. Last month Pepsi sponsored a campaign which dedicated 4 cents for every NYC check-in to CampInteractive, an organization that aims to inspire inner-city youth through technology.

This is clearly no playground game we’re dealing with here.