This is an update on the Webmail Notifier, a cheap chinese gadget that's nothing more than a RGB LED connected via USB. In this case, it's an especially cheap version that can only display 7 distinct colours, plus black (off).
Finally I was sufficiently annoyed to put the code into a “proper” kernel module (original module on kernel.org). Here's my patch that adds this particular LED gadget.
Here's the thing cycling through random colours: