Well to be able to have control over the volume slider / bar would be a step in the right direction for me.

And yes I know the volume bar would not be very accurate. My theory is to calibrate it once and a while (start both the slider and the receiver volume at zero). So I have to disagree with it not being useful, but I agree it won't be very accurate.

Maybe an idea would be to provide a sort of slider widget with decrease value and increase value actions.