... available for download here.
still pretty much in progress. works by monitoring the log file rather than the in-game chat... but as long as the updates are real-time, who cares about the technicalities :s
how to set it up: in game client, open the chat config window. direct all combat messages to one window. right-click on the name of that window and enable the "Log messages" option. (btw, the exact path to that log file can be found by picking the "Show log window" option in the same menu)
Once that's done, you can run the damage parser and point it to the correct log file. Then either add manually players to watch, or use the automatic mode to collect stats for everything nearby....
(was only tested with winXP, no idea if it works on anything else ^^;;