Querying the front application

FROM : Alexander Powell
DATE : Sun Jul 09 09:58:07 2006

I have tried to do a bit of searching to find a solution, but all of 
the old posts on this subject seem a bit out-of-date... so I was 
wondering:

Is there a currently recommended way for a Cocoa app to register for 
a notification or something when the front-most application changes?

After that's done, how could one query what application is now the 
front-most?

I have a need to write a simple faceless utility that only does its 
thing when a particular application is in the foreground.

Thanks a bunch!

-- A-lex