Indicator if an Avitar is IMing.

I'd like a feature where there'd be a meter or sign on an av's profile indicating whether they were IMing someone. Maybe even a meter, so if someone is juggling lots of messages the meter reads higher than if he's just handling one. That way I could see how busy someone was, so I wouldn't interupt him/her by opening an additional IM.
This could be a checkbox option:


For those who want privacy.