Well, that didn't take long. Just a couple of hours after the end of Google's I/O keynote, the Android TV remote control app has burst on to the Play Store. Download it now to control all the Android TV devices in your home! Which are none. Because Android TV isn't released yet. And won't be until the fall.
If you're wondering why Google even bothered to put the app on the Play Store in the first place, it's because it's designed for the developer kits currently on display at I/O.