"Twitter 360 is a new application specifically developed for the iPhone 3GS that enables you to visualize your Twitter friends located in your nearby environment, thanks to a unique Augmented Reality functionality using the iPhone camera.
Twitter 360 is one of the first iPhone applications to use the new Twitter's Geotagging feature to geotag your tweets. Please, note that Twitter 360 does not intend to be a fully Twitter client, our goal is to provide a different approach to the Twitter experience. We are already working on new ideas to be added in this application."
"In August  we announced that we were working on a new API that would provide developers with the ability to geotag tweets. Today, the Geotagging API is officially available.
This release is unique in that it's API–only which means you won't see any changes on twitter.com, yet. Instead, Twitter applications like Birdfeed, Seesmic Web, Foursquare, Gowalla, Twidroid, Twittelator Pro and others are already supporting this new functionality (go try them out now!) in interesting ways that include geotagging your tweets and displaying the location from where a tweet was posted. The added information provides valuable context when reading your friends tweets and allows you to better focus in on local conversations. Now you can find out what live music is playing right now in your neighborhood or what people visiting Checkpoint Charlie are saying today about the anniversary of the Berlin Wall. These are only the beginning and we are really looking forward to seeing the creative uses emerge from the developer community.
It's important to note geotagging is disabled by default for all users which means you will need to opt–in in order to use it. To activate the new geotagging functionality, go to your Settings page and click 'Enable Geotagging'."
(Twitter.com, 19 November 2009)