It's been little more than a year since Foursquare and Gowalla launched in the US, making 'social location' a geek buzzphrase, and popularising the idea of checking-in to bars, restaurants, tourist hotspots and even your own house.
They've grown fast: Foursquare now has nearly 1.8 million users, and has racked up well over 40 million check-ins.
So what's next for social location? There are plenty of startups working on cool apps with various twists on the Foursquare model, and many of them are already available on iPhone's App Store.
We've rounded up six trends, and a bunch of apps that show how this area could develop. See what you think.
Finding stuff around you
Foursquare is still mainly about finding people - seeing where your friends have checked-in and meeting up. However, several companies are focusing on social location as a way to Find Cool Stuff. Rummble - an app that predates Foursquare and Gowalla - is all about figuring out where to go next, while Flook (above) offers a beautiful postcard-based interface to find local secrets. iCoolhunt is a similar idea, getting its users to sniff out cool trends on the street, and upload snaps for posterity. Meanwhile, the Buzzd app aggregates check-ins from lots of social location services to help you identify which venues are jumping right now.
Shouting about the telly
There's an emerging crop of apps that apply the Foursquare check-in model to TV shows - i.e. the location element is your sofa, shouting about whatever reality show or football match that you're watching. Think of them as social TV apps. Miso (right) is a good example: you check-in to a show then share your thoughts, and which is launching Fan Clubs to give you exclusive clips and info on particular shows. Philo TV is another, which lets you earn points and badges as you go. Later this year, an app called Starling will let you tweet about TV and allow broadcasters to use that stream within their shows.
Getting freebies and offers
The most logical next step for social location apps is to give you tangible rewards for your check-ins - something Foursquare is already trying by getting venues to offer discounts to their Foursquare mayors. However, there are already dedicated apps for freebie-hunters. Loopt Star, which is US-only for now, lets its users get discounts for checking in at The Gap, Burger King and Starbucks outlets, as well as free MP3s from Rihanna, Lady Gaga and other artists when checking in at certain bars. There's also Pepsi Loot, which offers more free music and discounts on fizzy pop at a range of US restaurants when you check-in. Later this year, an app called Shopkick will roll out more discounts for check-ins at other stores.
Making it more of a game
Foursquare isn't the biggest social location app in the US, despite the hype. A separate app called MyTown (right) signed up its two millionth user in May, and its developer claims those people spend more than an hour a day each using the app. Why? It has more game elements: it's like real-world Monopoly, where you can buy and upgrade the places you check-in to. Meanwhile, a newer app called SCVNGR is all about creating location-based gaming tasks, often in shops, based around completing challenges. The theory in both cases is that game-like elements give people more of an incentive to check-in and keep checking-in over time.
How about social location and dating? It's an underexplored area, with some well-founded concerns around privacy and stalking. However, there are some apps emerging that are looking to offer social location dating. StreetSpark is a good example: it gets you to fill out a profile, then pings you when someone's nearby who might match your interests. You can then chat to them and arrange to meet, but your location is never given out until you agree to. Another location-based dating app is FlirtMaps, another free app that lets you hook up with other singletons via a map-based interface. If this kind of thing takes off, expect the big online dating agencies to pile in with their own apps.
Sharing stuff with other people
One of the most intriguing social location apps this year has been LoKast (right), which lets you connect to other iPhone users nearby and share photos, video and music (well, 30-second preview clips with iTunes Store links in the latter case - it's not a pirate thing). The idea is to get people in the same place to start sharing media, and bands are using it too to distribute free songs to fans attending their gigs. Even Apple may be working on something similar: a patent filed by the company earlier this year for something called iGroups involved an app that lets people attending the same concert or event share information and content.