idle exit hook

[Ergus]

Hi:

I recently saw a question in reddit but the answer there was not
clear (or maybe it requires a feature request)

Is there an idle-time-exit-hook or, what's the canonical method to call
a function after breaking an idle? something like on-idle-exit?

So far I understand that having such a hook could produce some
performance penalty but not more than post-command-hook for example. Any
way, adding some restrictions (running it only once || reset the
hooks list on every idle start/end or just documenting it properly)
could solve the problem.. does it makes sense?

Best,
Ergus