Twitter Powered Traffic App (app store link)
BNE Traffic is an iPhone application that displays traffic incidents around the greater Brisbane area using information from hundreds of Twitter users using the #bnetraffic hash tag.
The application uses Google Maps to display information about current traffic conditions. The markers on the map show where traffic obstacles have been identified.
As its name suggests, Stalqer is an iPhone application that will let you follow the movements of other people without their express permission.
Stalqer connects to your Facebook, Twitter and Foursquare accounts and can display a Google Map of your friends based on their location sharing on those services.
Stalqer can grab location data from (public) Facebook profiles, geo-tagged Tweets and from Fousquare.