[imp] Display a global status message

[Gary Smith]

I was wondering if there is a simple way to add a global message to all pages for announcements?  Typical for outages we send emails to all of our users but the problem is 25% of the users use horde whereas the rest use think clients.  Anyway, I would like to post announcements on the pages when we are doing things like outages/upgrades. 

Any advice on this?