Shortcut to symmetry?

Is there a way, outside of individual adjustments, to take a simple object and make placement/angle adjustments while at the same time having another object mirror its movements? Like having a left arm in the exact opposite position of the right arm with all twists and turns applied.
Comments
You could set ERC links between the two, with a -1 multiplier, but that would go one way only - it wouldn't let you work on either side and have the other follow, you'd have to pick one. You can of course use the Symmetry command after the event (though if you are using Pose Controls rather than the transforms on the bones themselves you would have to Bake to Transforms first).