The style of 'monitoring for activity' that Konsole uses is not quite what I'm looking for.
For one thing, it requires user interaction to activate it. So you gotta want it bad to do it.
For another thing, it makes a huge deal out of the activity that it finds, firing the window-manager hint and everything. (and that's why it requires user-interaction to activate)
I propose to keep this feature, but add a more pasive one that is always on. (I got this idea from iTerm, for the Mac).
When activity happens on a tab, turn the tab's name purple (or put a * in its name or something). It stays purple for a couple seconds after activity, but then turns red if silence happens. These behaviors are not triggered if you're on the tab, cuz you can see the changes with your eyes.
It's nice and passive, is convenient to always have on, and it notifies you of multiple states: Activity and silence.
That's what I'd like to see.