At least with GAIM, you can configure the Idle/Away in two ways to get close to what you are talking about. At least in X, you have the choice in the Preferences-Away/Idle panel to set "Idle Time Reporting" as { "X Usage", "Gaim usage", "None" }. I believe the same is true in the Windows port. And then there is the default "I'dle Mak'er" plug-in for more control over idling.

Interesting. That's good to know.

Is it possible to have application specific away settings? Like if I'm in Keynote, Pages/Word, or my IDE for more than 10 minutes with steady input, set status to "Away"?

That's the kind of thing I could see being seriously useful.

RE: Meet the Life Hackers - New York Times