I got a 4th gen Apple TV Developer Kit last year in September but I was working full time on Caff and although I wanted to play with it I couldn’t wrote a single app for it before Christmas. Nevertheless I used it for a couple of months, mainly to play media content streamed from my NAS and I missed a way to add movies and TV show to my Trakt.tv watchlist directly from my Apple TV (there are a couple of ‐pretty good‐ media players which sync with Trakt.tv, but none of them allows you to add content to your watchlist).
So I wrote Trakt.tv Browser an extremely simple App that just does it: you can search movies and TV shows and add or remove them from your watchlist. I plan to update it with more features as I use it and find that they are useful but it is a hobby App for the moment so it will take me some time to publish any update.
Let me know any feature you’d like to see in a future update in the comments.