A BlinkStick is a USB powered LED that can be driven via a simple API from a programming language like Python. Since the status of an ElasticSearch cluster can be determined using three colors (green, yellow, red) a BlinkStick can be a nice visual aid in your monitoring infrastructure. An easy proof of concept is to use the BlinkStick Website API that allows, given a token, for the color of your BlinkStick to be set remotely by your monitoring system for example. You can find such a proof of concept here: https://github.com/a-yiorgos/elastic-blink
Of course if you want a more elaborate and secure setup, it is possible. I had my 15 minutes of fun. YMMV.
I was showing the BlinkStick to kid today and after a few blinks, I decided to make it speak Morse code. It was fun and quick, for I did not have to start from scratch. Morse code on a LED has done the same thing using a Raspberry Pi and a LED (I used their Morse code dictionary).