Albeit a little different then what you asked, but maybe
Telepathy could come in handy?
AFAIK,
VEM can share multiple timers with your raid, but has been abandoned for the time being.
There is a soundpack for DBM available however.
And IIRC, in
DXE you could create timers which would respond to events and share them with your raid / someone else, but that also has been abandoned.
What kind of boss do you need this shareable timer for and why?