Runeaudio is so great because it makes you lazy. You don't have to turn on your tuner, you don't have fiddle around with CDs and LPs. Yet I still have to turn on my amplifier by hand!
Is it possible to set a GPIO pin high when music is turned on and make it low when the music is off for a certain time? The time before it is set low again could be configured from the 'settings' menu for example.
Using some prototyping board I can easily create a circuit to control the power if my amplifier, based on MPD playing music or not. I have to add a switch to overrule this for when I like to watch TV for instance.
If there are a lot of people interested we could make a dedicated PCB for it.