Screencast of the addon: http://www.youtube.com/watch?v=f5AxA8vpC8Q
1. Only works with Firefox Nightly and Aurora 9
2. Due to a bug in the platform, it is impossible to update your location once a getCurrentPosition() call opened a permission prompt, see bug 688465.
To work around this bug, update your position before being prompted for permission. Reload the page if necessary to display the permission prompt again. A bug fix has already landed in nightlies and will be available to everybody in Firefox 10.