Py IPO Drivers for bones?

Sorry if I am not well informed. As I know there were introduced python IPO driver in Blender some time ago - http://www.blender.org/development/release-logs/blender-240/ipo-drivers/

For one python line I can use objects inputs. My question is whether python IPO drivers are ready also to work with bones of armature as a source data.

For example if I want my object to be driven by Cube Loc X I can just type on line python expression ob(“Cube”).LocX

But can Blender handle the case when instead of a Cube I want to use the value Loc X of a Bone.001 from an Armature.001 for example? Is this possible? How should the python line for IPO driver look like?

The thread moved to Python forum.