I have zero experience with the Afterburner app, but my instinct tells me you can't. It probably uses protocols similar to things like the Google Chromecast. It's a whole lot cheaper to make an application that listens for appropriate signals locally. To make something work over the internet like that, they would have to make (and maintain) a server specifically to facilitate people logging in and communicating with their computers.
There would be no RoI for that kind of thing, as nobody would pay for it; and I'd guess very few people would even want to overclock their computers without being present to see the results.