(note: posted on the Curse forums then saw your note about requesting enh here)

If plausible, it would be even MORE amazing if you would display enemy players in PVP zones.

Carbonite does this on a large scale by enabling a hidden chat channel so that Carbonite users can send each other enemy positions. I don't know if you could hook into that channel (in Carbonite it is in the Social options, "Punks" window), but if so you could even use that data for more notice. "Punks" is the last thing from Carbonite that I really miss and your Addon would be a much richer way of displaying it.

But even without Carbonite's extended data, a basic display of someone in your DIRECT vicinity would still be very helpful. It may turn out that Carbonite doesn't transmit X,Y for enemies (though I'm pretty sure I've seen them on my worldmap, so it must).

The PVP targets should probably have some pulse options just for attention grabbing.