So I thought I'd share the TinyURL callback API I wrote.
The API url is: /tinyurlapi
Here's the source code for your own hosting: /downloads/tinyurlapi.php
There are full instructions and examples on the page along with a demonstration.
Note that since creating the script, TinyURL have changed their page so we can't create tinyurls on the fly (though we can still look up), so I've plugged in is.gk instead for creation.