Yes! I created such a rule and added it to the examples page:
http://groups.google.com/group/personalizedweb/web/examples
It will function on all web pages (including HTTPS), and as a side
effect, you will always see the PWeb icon in the address bar (because
all web pages will be modified). Of course, you can limit the set of
the web pages that will be affected by this rule by tweaking "Match
URLs" and "Exclude URLs" patterns. If you don't want HTTPS pages to be
affected, replace "^https?://" to "^http://".