WPF: Getting source of a Binding

Question

I have a reference to a Binding instance, which was defined with an ElementName in XAML. How can I get, at runtime, the actual element instance being the effective Binding's source?

The same question holds for bindings with Source, implicit DataContext, etc: how to I get the effective source, given only the Binding instance?

And, if may I, how do I get the effective target?