We use a old traffic signal powered by a Raspberry Pi to similar effect. We have found it quite useful in providing timely feedback and encouraging the quick resolution of issues.<p>You can see pictures and source: <a href="https:&#x2F;&#x2F;github.com&#x2F;tantalic&#x2F;build-light" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;tantalic&#x2F;build-light</a>