I read a blog post last year from Mountain Goat Software about the importance of feedback devices in an Agile workspace. They serve to reinforce a sense of "one-ness" when the team gathers together to solve mutual issues such as Production fires, or when builds are broken.
Here's what one of our teams started doing when emergency issues arise in our Production environment:
1. The Scrum Master for Team Ramrod (yes, it's named after a transformer) posts a sign at the entry point to the team's sitting area indicating to a would-be visitor that the team's busy fighting a fire.
2. And, in the spirit of visual queues, we put a virtual fire on the projector wall in the team's sitting area: