At one point, I tracked every context switch during my work day. I kept a legal pad next to my mouse and I would write down the time whenever I switched between coding, emailing, surfing, talking to someone in my cube or walking around to find someone I needed to talk to.
People thought I was odd. They’d ask what I was jotting down when I noted my context switch, so I briefly explained it. “Okaaaayyyyyy?”, they’d say. An unintended side-effect was that people did end up bugging me about random things less. In fact, it was way more effective at that than putting up a sign that said “unless something is on fire, email me”. So it goes.
I never ended up running any aggregate numbers on the data. But, it did give me an idea about the frequency and cost of my context switches. I wish there was a better way to track this sort of thing passively. I’m sure it would still shock me how much time I go in and out of focus.
If you’ve never tried this sort of experiment, it’s worth running for a week or two. You’ll almost certainly notice something worth trying to cut out by glancing over the list of things you’re spending time or wasting focus on.
Adam Keys is typing 
Hey Adam, have you seen RescueTime (http://www.rescuetime.com/) ? It’s a passive solution to what you describe here. I know it picks up every context switch on the computer, and I think you’re able to input when you’re AFK, etc.