Ask HN: Physical status indicators in your office

So most of you will probably have a LCD panel in your office to display live status, such as build status, system monitoring etc. Now that is fine for large floors, but a bit overkill for many 2-3 person rooms and simple, discrete metrics. Also, I love physical indicators. Our Nagios system controls an old traffic light (from Ebay) using a Pi. It was fun to make, but also a lot of work. Ideally, I'd order a bunch of physical indicators and all my employees get one to hook up to their primary target.

So what do you have in your office to indicate live success and failure, apart from monitors? What works best for you? What was the easiest to implement?