Just after midnight BrightKite, a location based social network launched out of their private beta into an open registration. In their words:
Brightkite is a location-based social network. In real time you can see where your friends are and what they’re up to. Depending on your privacy settings you can also meet others nearby.
Location checkins are done attaching you to businesses, cross streets or user defined placemarks. Notifications of nearby friends checking in happen via email, SMS (international too) and via their web interface. Users can directly message each other via the iPhone app or txt message, without exposing phone numbers.
Privacy is always a huge concern with anything dealing with location. BrightKite has some pretty advanced privacy features. You opt into each checkin and opt to share it with trusted friends or the general public.
One of the most interesting features is the BrightKite wall, where places can display all of their recent check ins, photos and notes via fullscreen flash (imagine this at a concert or coffeeshop). Users can check in and join BrightKite via txt message to the wall.
I’ve been using their application for a year now, and have found it to be incredibly compelling. Their developer API is open, and robust (their iPhone app is built on top of this). Here is a demo from their iPhone app, a new version is expected soon:
Disclosure: I’ve known the BrightKite guys from before they were accepted to TechStars, where I work.