Show the big clock in tmux after N time of inactivity -

the big clock can activated with:

t  big clock 

is possible monitor inactivity , use screensaver?

this possible introduction of hook feature in tmux 2.2 & 2.3 (tmux change log)

you should able trigger clock appearing after window has been silent period of time. monitoring user inactivity still not possible.

you can set window option monitor-silence & use alert-silence hook start clock.

see tmux 2.3 man page hooks & monitor-silence.