This idea is pure genius:
“We used to work on a team with a vocal interrupt protocol: if you wanted to talk, you would say “breakpoint Mary” where Mary was the name of the person you wanted to talk to. If Mary was at a point where she could stop, she would swing her chair around and listen. If Mary was too busy, she’d just say “ack” and you’d go on with other things until she finished with her current head state.“
–Team Geek: A Software Developer’s Guide to Working Well with Others