I've used on of these. Really helps that guy get a hint and leave you alone when you're trying to get work done.
http://heeris.id.au/2013/this-is-why-you-shouldnt-interrupt-...
This would be great if you need a way to 'close your office door' in an open layout office. Nice work.
Simple battery powered light that you can use to tell your coworkers to leave you alone when you need to focus.
I'm doing the hardware design on this project, and having a lot of fun doing it. We're excited to have the signs out there for people to start using!