ANONYMOUS  ...and, of course, you are going to shae this?  
(Version 1.2.7)

STICKMAN67  I just love these "I can whip up four lines of code to do the same thing" kind of comments.

Mate, I can't, so I'm quite grateful for the efforts of others who do.

And can your four lines of code renice on the fly? I wonder.

Not everyone is a gun software author. Not everyone is a terminal command-line genius. Not everyone has the time or inclination, or even the desire, to be so.

So for developers who take the time to write software, test it, release it, upgrade it, iron out the bugs, respond to their customers -- all of which this person has done -- and then charge a very modest fee ($8.95 is peanuts in this day and age, and for an extra $1.05 you can have Renicer and Tiger Cache Cleaner).

Yes, there are free utilities that do similar things, but that's the prerogative of their authors. If you don't want to pay, great. And if you want to write your four lines of code and use that instead, please feel free. But don't bother to burden us with your griping. It's not clever, it's not original, and it's certainly not educational or interesting. In short, it's a waste of your time and mine.  
(Version 1.2.7)

ANONYMOUS  Applescript to the rescue!

Punch this in to Script Editor run it. You can even save it as an app, but you'll have to force quit it.

repeat

tell application "System Events"

set currentApp to item 1 of (get name of processes whose frontmost is true)

end tell

do shell script "sudo renice 0 -u YOURNAMEHERE" password "YOURPASSWORD" with administrator privileges

set currentPID to do shell script "ps -axww | grep '[/]" & currentApp & "'| awk '{print $1}'"

do shell script "sudo renice -20 -p " & currentPID password "YOURPASSWORD" with administrator privileges

tell application "System Events"

repeat until {currentApp is not item 1 of (get name of processes whose frontmost is true)}

end repeat

end tell

end repeat (11/20/2003, Version: 1.0)  
(Version 1.2.9)