Yep. Here's Google on your desktop. It searches Outlook and Outlook Express email, Internet Explorer, AOL IM chats, and all the MS Office formats.
Check out John Batelle's Searchblog for an interview and more cogent analsis. I'm just sad I can't use it (although I suspect third-party APIs will mean a ton of applications in the next couple of weeks). Hmmm...Google Image search that automatically checks Flickr as well...
Second "hmmm": imagine Zoe, except implemented as Google Desktop for the Mac: iPhoto, Address Book, Mail, etc. etc. all with intertwined search results.
Do you think Google is working on this for the Mac? Somehow, I doubt it. They'll get a bunch of this functionality "for free" when Tiger ships (so if they are working on it, they'll make sure it ships with Tiger). But given Jobs' pitching of Spotlight, it may be up to a third party to tackle this.