Change Details

So when I'm OoO, I put a notice on some of the wikis I'm mostly active on. Recently I appreciated the chance to put it on my user page at Meta, so that it would also show up at dozen other projects, and some people did notice it. But people do not usually check my user page at Meta before sending me a message onwiki, and I also have local user pages at so many Wikipedias. So a global talk page edit notice, or some kind of popup warning, would be way more effective for things I need people to know before they leave a message for me. I'm wondering if there's already some code I could put somewhere to achieve what I want...?