Here's some brief information about the widget:

Carriers
I'm willing to add support for the major carriers in the U.S. The PHP source is published and I will be publishing the widget source code if any international folks want to write support for their own postal systems.

Cache
The widget uses 3 levels of caching: The Chumby will cache all tracking data internally as a Mobile Shared Object with a 10 minute expiration. The public RSS tracking server has a 30 minute cache interval, but this can be lowered if you configure the PHP script and place it on your own server. Finally, the PHP script sends the correct Last-modified header, leveraging the Chumby's built-in HTTP cache.

Alert
The alert isn't really documented in the widget configuration but basically when it's checked, it will sound an audible alert "You've Got Mail" when a package status changes from in-progress to delivered. The alert should only sound once, but will re-occur if you reboot the Chumby. I may add the option for custom sounds and persistent notification alerts in the future.

Why the need for a PHP script?
Currently, the PHP script is responsible for translating the HTML/XML tracking data into RSS format which is readily parsed by the Chumby. This takes some load away from the Chumby and also extends the options for caching. I could use the XML-RPC systems that most carriers provide to have the Chumby communicate with the carriers directly, but each carrier currently requires a user to register for an API key which is a step I'd prefer to avoid. Another show stopper is that most of the carriers (if not all) seem to be lacking the necessary crossdomian.xml file.

Interface
The text will scroll using the accelerometer as well as by finger touch. The timer for moving between multiple packages gets reset whenever a person physically touches the screen, allowing for more time to read tracking details.

Privacy
For maximum privacy, download the PHP script and run it on a local server or web host. The PHP script offers some security to those using the freely provided tracking server (http://chumby.freehostia.com/track.php) by using a one-way hash to store the cached tracking data files. This eliminates the need to store tracking numbers anywhere on non-chumby.com servers.

This would be seriously cool.

Great widget, but I'm having a problem getting it to display tracking info when running the PHP script on my website as opposed to the free tracking server.

I followed the directions carefully - changed the filename to track.php and uploaded it to my webhost in its own directory. Created a directory within that directory called "cache" and gave it 777 permissions. Downloaded crossdomain.xml and stuck it in the root directory of my hosting account. There appear to be .xml files in the cache directory, but the widget on Chumby says that the tracking numbers are invalid, expired, or not yet in the system (even though these are UPS tracking numbers that do work, because I can look them up on UPS.com.)

Any idea what I might be doing wrong?

Thanks for the reply. I looked at the .xml files on my host, and they just said the same thing that the widget said (tracking number invalid, etc.) So I changed the widget back to the free tracking server, restarted the Chumby, and the widget did correctly display the tracking info for both of my 2 tracking numbers. Following that, I copied your code to a new track.php file, and replaced the one on my host with it.  Then I changed the widget to point back to the location of the file on my host again. When I did that, the first time Chumby loaded the widget, it played the "you've got mail" sound, but the display said that the widget wasn't configured correctly. Then, it just displayed "undefined" on the screen.

I guess I could use the free tracking server, just not sure what the security issues would be (if any).

is it possible file_get_contents for URLs could be disabled on his server? You could use cURL instead?

A simple phpinfo() should give you all the information you need?

Check the values for allow_url_fopen

I stand corrected

Hehe it looks like gingerbeardman was right =]

Lloyd, can you try creating a phpinfo.php file? It should contain the following:

<?php phpinfo(); ?>

Open the phpinfo.php file in your web browser, you should see the value "disabled" to the right of "allow_url_fopen". Search through the document and look for "cURL support", if it's present and the value is enabled, I should be able get the tracking script to work with your web hosting environment.

If cURL isn't present or is set to disabled, it's still possible that I could get it working by using raw sockets or by overriding your PHP config using .htaccess or ini_set().

Awesome, try using the updated script: http://cyphergate.com/track.php.txt

Please ensure your browser didn't cache the older script.. You should see the new configuration parameter, retrMethod, which is set to use cURL by default.

Great, glad it works! =]

I've updated the widget and the alert checkbox is now working on my end.

I could add functionality to prevent it from going off at a certain period in the day, however, I will have to reactor the configuration widget. This may be something I add after I complete the map/visual tracking features.

Thanks for reporting that hayes, I've updated the widget and it should now allow for any spaces.

I've done some experimenting with mapping package locations and was able to get G Map, which is a flash-based Google map implementation, working on the Chumby. For now, I've posted this as a standalone Google Maps widget (pending approval) and I will be experimenting with some interface layout options for the package tracker itself.