Theres an addon for that valled VanasKos.

Also Carbonite has a punk alert that will mark where other Carbonite user have seen the "enemy." That can come in handy from time to time letting you know where the bad guy is and that you should go with care, or just not go at all. I don't really know how much skill there is in leveling on a pvp server per say, but i know that if you do happen to turn the tables and kill your would be ganker to get ready to move quick because they will be logging onto their 80 soon and coming after you. :)

Recently I've found that the Peggle addon significantly reduced my ganking deaths.

Seriously though, having gone 1 - 80 on a PvP server this year i've found the best addons to be Carbonite for "punks" and FriendsWithBenefits so that your alts can automatically call for help from all your high-level friends.

But nothing frustrates a camper more than sitting there without getting to kill you - and knowing that you are online (there's a mod for that too, which tells you if the player has logged or if still floating around) - and a good round or two of peggle is usually enough.

When playing on a PVP server, Carbonite punks list and another addon, WatchTower are awesome.

It hasn't been updated in ages, but it's great for quick alerts to LocalDefense (or BG channel). I think it still works... it's been a while. Just watch your settings and don't spam.

http://www.wowinterface.com/downloads/info5393-WatchTower.html