[O] Follow mode to also narrow buffer

[casedeck]

Hi all,

apologies if this was asked before, I couldn't find it.

I would like, when using Follow mode in the agenda view, to have the other
buffer (opened through Follow) be immediately narrowed to the current
subtree (through function org-narrow-to-subtree). 

So, the Follow-mode would not show the whole agenda file (centered to the
selected item in the agenda), but would show only that item and it's subtree. 

Ideally, if the current item is a subtask, the Follow mode would also show
the parent task abbreviated (with "..."), and it's parent if it exists, and
so on until the top heading marked with a todo keyword is shown (I guess
that could be called org-narow-subtree-with-above-tasks or similar) - but
I'm not sure this is achievable...

I suppose just the buffer narrowing can be done (probably quite easily)
through some hook or something, but I (yet) don't have the skill to write
that code myself. Can anyone help, please?