Both ES Explorer and Retroarch (as well as others) will install perfectly via the play store. Just find your game/app on the play store, click install, and choose your AndroidTV device. Have only tested with the ADT1.
They will show up under chainfire sideload launcher http://www.androidpolice.com/2014/10/23/chainfires-sideload-launcher-lets-android-tv-users-easily-start-sideloaded-apps/
We’re proud to announce that Haystack TV has been chosen as a launch partner for Android TV. The app is now live and available on your Nexus Player or other Android TV via Google Play. If you have a Chromecast you can also stream to your TV from your Android phone or tablet and also from your iPad.
Haystack TV lets you watch headlines news from multiple sources. We built the app because we were frustrated by the lack of news choices we had after cutting our cable subscriptions. In addition to current events you can watch the latest in science and technology, business, sports, entertainment, or even late night talk shows.
By the way, Haystack TV was conceptualized because of feedback from the Reddit community so thank you!
Read more about the release at the Haystack TV blog.
Has there been any info on a non Nexus Player Android TV device? I really want to combine Chromecast, native Plex and Limelight in the one device. But to efficiently stream games I need (or maybe just want) a ethernet port... So is there any concrete news on an Android TV with an Ethernet port?