Universal configuration across models for acts_as plugins?

I’m writing an acts_as_watchable plugin so that people can subscribe to
model objects and receive email when these objects are updated. (If I’m
duplicating effort, please let me know.)

There are some things that I’d like to configure on a system level, say
for example the “From:” header in the email, or perhaps a subject
prefix. Is there precedent for doing global configuration like that for
an acts_as plugin, or would a different model be more appropriate?
Thanks all.