Apple has been keeping a tight leash on the third generation of their Apple TV hardware. Not only has it stood up to every attempt at a Jailbreak, but they don’t allow 3rd party applications through the app store like the other iOS hardware does. The second generation hardware was a popular platform for XBMC. It required a jailbreak to load the home media software which is why it can’t be done on the newest box. But here’s an alternative. This hack uses DNS redirects to make Apple TV 3 a Plex frontend.
Instead of putting new software on the Apple TV this uses a separate computer to intercept its web traffic. You aim your Apple TV DNS at the computer running the script, then use the native Movie Trailer app, which will be populated with movies and TV shows from your Plex backend. All other functionality will be retained, making for a near-perfect solution. For more info on the system check out this forum.