Well I'm sure someone else is doing this too, but you can try your luck.
First, you need to go into the settings of your gmail account and allow for POP3 access to your messages. You should also make sure you have it configured to "leave messages on server" when they're downloaded, otherwise reading them will delete them.
Check out poplib for retrieving the messages.http://docs.python.org/library/poplib.html
You'll need to iterate through the messages, perform some match against the subject line/message body. Parse it for the url, and then you can use httplib. http://docs.python.org/library/httplib.html