Unfortunately, I am not aware of any software that will easily do mouse broadcasting on the Mac. I always had to use key binds and macros for my healing.

Synergy may broadcast the mouse (i have only used it for keyboard broadcasting) but I believe it will only broadcast to another computer and not the same computer. Maybe you could get around that by running the server and the client on the same computer? I never tried that myself.

I think owensd was working on adding some features to plexor for network support, but i don't recall anything regarding mouse broadcasting.

you can read through the post here
http://www.dual-boxing.com/showthread.php?t=23541

I wish i had some better answers for you...