New in 2.77 buildbot: a new way to create drivers.

I over heard from the blender podcast 19 on a new way to create drivers, and it seems that it is cool, but i really haven’t been able to make it work from a different bone or object from the one currently selected, which to me doesn’t seem all that useful, didn’t find any documentation on it either.

Can anyone give me a hand?

Could this brand new commit be seen as what you were looking for?

Also, I think the lack of documentation tends to be quite common for fairly new features, keep in mind that they are still working on getting 2.77a released as well.