The last time I was there, I used my wife's iPhone with the "Remote" app, and was able to completely control the AppleTV from two floors up. Very cool. Sadly, there isn't any such product for Android.
Actually, come to think of it I believe there are one or two apps for controlling iTunes. Sorry to mislead. Nothing for AppleTV yet, though.
I assume you've already bumped into the
Android DACP client. It's open-source and all that, and appears roughly equivalent to Apple's Remote app. I've been pondering a jump from my iPhone to Android, given the potential coolness of the new Googlephone, and this was one of the required features for me.