Hey bob,
I use an pad myself, but have tried
Irule
Demopad
Roomie remote
As well I have found lots of apps built by the manufactures to control AVR's.
And the are cool apps for the iPad that will control the music server. This way I ca not only change my avr to zone 2 while I am in zone 2 but also queue up new music and change albums that are loaded on my server.
I feel I am just scraping the surface and there is lots we can do now.