PlexConnect is a simple DNS server that rewrites requests to trailers.apple.com to your local machine (where a daemon is running that responds to requests from your Apple TV.) It then takes the place of the "Trailers" app, and requires only that you change your AppleTV DNS server config to your own machine, and that you install their SSL certificate in your AppleTV's certificate store.
You can edit your AppleTV's certificate store with an Apple-developed program called Apple Configurator (in the OSX App Store for free) so at least it doesn't requires anything like jailbreaking.
Uh, holy crap??? That's amazing. I hadn't even thought of trying something like that. That's brilliant and ingenious. At this point I'd just resigned myself to transcoding where needed (usually just need to change the container, which takes one ffmpeg command, and about 2 minutes for a one hour video) and let iTunes handle everything, but I have a major soft spot for Plex and miss using it. That's just phenomenal. gushing.stop();
Another interesting option is Beamer[1]. Bought it a while ago and I have nothing but good things to say about it... Just drag any video on it and stream it to your AppleTV in seconds.
I just visit put.io from my iPhone or iPad and from there I stream the video and send it to the Apple TV via Airplay. There's also a couple of free 3rd party native iOS apps that let you connect to your put.io account, and stream the videos, but they're not really necessary. Never had much luck with AirPlay mirroring with my Macbook Air, it's always laggy in my experience.
So yeah, you do need either an iPad or iPhone to do it, however Put.io has a Roku app if you have one of these.
