This app was mentioned in 7 comments, with an average of 1.14 upvotes
I might be far too late, but...
Allows you to control your iTunes library over wifi from an Android phone. Only application I've ever donated to, and it works flawlessly.
If you are playing from the Music app on a Mac then the Remote app does this. You could use an old iPhone or iPod Touch for this.
I use an old Android phone running Retune and Spotify to do the same thing. Retune does the same thing as the Apple Remote app, and Spotify allows you to control what is playing from another device.
Retune for Android allows multiple phones to access the same iTunes library, so change the playlist, tracks etc, and also adjust the volume of airplay devices such as the AppleTV. You can use it to send anything in iTunes (movies, podcasts, music) to the AppleTV.
It won't however let you control other aspects of the AppleTV, but maybe it is enough for you.
Retune won't do everything but allows you to send content from iTunes to play on Apple TV. It's the best app for controlling music play back from an Android phone to Airplay devices IMHO.
Haha yeah, just thought of it while I was typing it actually. It works great, I'm using this app. Hopefully I'll still find a way to be able to do what I initially needed to do since the app only limits me to music and not other things.
I use Retune. Also on a Mac. I'm happy with it, though admittedly I don't use it often.
Retune works very well for that...