This application merely allows you to post a tweet and update the 'location' part of your Twitter profile at the same time. Then, you can share your location information and twitter activity with anyone, on a map page or via a geoRSS feed. If you leave the field empty, your location will be updated but no tweet posted.
Map
You can see the history of your tweets and locations on a map, with a path drawn between the locations (in order). To destroy this information load the application with this link
Disclaimer
This is a test app. It's not part of Twitter. It gathers personal information. Use at your own risk. You may lose data, it may not work, Twitter may be down, etc. Any questions please email Ben Clemens.
Privacy
This application saves your Twitter password to a cookie on your local device only, mildly encrypted. Your username, locations, and tweets are stored on my secure database, to draw the map (see below). If you are uncomfortable with this, bookmark this link and the app will not store any information locally or remotely. I will never have access to your Twitter account, and all the information stored is public already (unless you've set your tweets to private by default).
Credits
Thanks to Matthew Krivanek for his beautiful deconstruction of how iphone style buttons are made in CSS, and Monte Ohrt for GoogleMapsAPI in PHP.