Not trying to be snarky, but did you read the article or did you skim it? The author explains the reasoning behind the walkie-talkie approach versus a phone call.
he does but I am not sold on the benefits. A slack message "can we talk, call me" would be async and non-distracting (just turn off slack alerts when you want to focus). Using an online call rather than on/off (like a walkie talkie) then seems much of a muchness.
Yes, and setting your status to "in a meeting", "away", "code sprint", etc. is helpful. These are things that could be automated, I'd consider that a better approach to the problem.
Let people know subtly you don't want to be disturbed unless it's important, otherwise you will be.