This similar method was mentioned by a couples on here before but because their English wasn't too good they couldn't get the point across. Hopefully I can.
Generally, the Apple Trailer app within your atv 2/3 basically just loads an xml file from http://trailers.apple.com/appletv/index.xml and display the content according to that xml file. Well some of the Chinese users figured out that if they changed the DNS so that trailers.apple.com points to their own IP they can load their own custom xml file and have the atv load whatever they wanted. I essentially was able to replicate this on my local machine and got the apple tv to load my custom streams and videos. What I did was go into my router and added a setting to my router to assign trailers.apple.com to the local IP address of my web server and I created my own xml file within my local website. I was able to load a lot of the popular live streams for xbmc like HBO HD etc.. and play some video files, but I did find that it uses the native atv video player to play them so this means it can only play standard video files that the atv can play like mp4 files but it didn't play flv or mkv files.
To get this working you don't need your own web server. you just need to put your custom xml file on a website change the DNS so that trailers.apple.com points to the same ip as the site that contains your xml file and it should load. oh you also need to place this js http://trailers.apple.com/appletv/application.js file in the same directory as your index.xml file
I confirmed this works on a Non-jailbroken apple tv 3