Well, the bad news is that the blurb in the Slingbox FAQ and User's Guide is meant to say that you can connect a Mac to your Slingbox, and if it has Front Row and an IR sensor, then you can control that Mac and watch its output remotely via SlingPlayer (or Sling.com), just as you would normally do with a cable box, DVR or such. Instead of using the Slingbox to change channels on a cable box, you'd use it to navigate Front Row on that Mac. The Slingbox IR cable would hang in front of the Mac's IR port, instead of the IR port on a cable box. That's also why it says that you don't need the Apple Remote, but would need Front Row and an IR port on the Mac.
You can do likewise for AppleTV:
HOWEVER, there are indeed Front Row plugins, and if anyone had a bit of programming experience and free time, then they might be able to do for SlingPlayer what others have done for Hulu, Netflix, EyeTV and such:
I Googled for way too long, and to no avail, looking for a SlingPlayer plugin for Front Row...
The closest I got was this involved hack to get it to work with AppleTV:
GEEKY NOTE: Front Row uses almost (but not enough to make it identical) the same codebase as AppleTV, but people who have tried to take AppleTV plugins and simply put them into Front Row found that they do not show at all in Front Row.