So, I don't know of anything like this offhand, but if anyone knows of something, I'd love to know of it.
What I'm interested in is an addon which determines if you are
outside of an instance/raid, and if so performs a /who <mouseovername> when you roll your cursor over a corpse.
Basically, I'm a nice person when I'm on a rez-capable class, and every time I see "Corpse of SomePlayer", I stop and do a /who. If they are online, then I rez them and heal them up.
As you can imagine there are a TON of random corpses lying around from players who died and decided to log out from frustation or something. Because of this, I don't often find one which is actually still online. Even so, I find myself stopping every time when I encounter a poor soul, "just in case", and it leads to much time wasted doing /who's on these corpses over time. An addon such as this would make my life easier and much more pleasurable.