Enterprise Manager would certainly do the trick, you could perform a search on the EM for the IP with ease.
A cheap alternative would be to use a simple program (there's loads out there) to pull the configuration from each every day and place the files in a single folder. You can then do a search for the IP on the contents of the folder (using grep in Linux, Windows Explorer search whatever) and do it that way. Easy.
Neither will give you a fancy map mind, but I'm sure that's possible too using iControl, if you have any spare developers hanging around!
Nimbostratus
