Sounds interesting!

I haven't looked yet but Super Search may yield some interesting answers.

Pointers:
You'll want to use a cookie jar.
Look into parsing the XML version of the Newest Nodes.
If this will only be used on a windows system, look into Win32 for the MsgBox function to do your alert box. It's very handy.
For a more cross-platform solution, Perl/Tk would probably be the simplest for creating an alert box.