How to make hardstatus shows activity of window?

[Chan Wai Wa, Raymond]

I am currently using the followings setting to make hardstatus show
current window list and highlight the current window.

hardstatus string "%{.bW}%-w%{.rW}%n %t%{-}%+w %=%{..G} %H %{..Y} %m/%d %C%a "

I searched for the usage of this but has no result, do anyone know how
to modify the string to make it shows sth to let me know which window
has activity like what i see when i press "^a w"?

Thank in advance.