Codes are used to send secret messages. But, they're used for lots of other reasons: efficiency, accuracy, reliability, and identity. Internet protocols are a type of code. The images and the music you watch, and the clothes you wear are another type of code that expresses your identity.
This project comes from a workshop I taught at the Portland Maker Faire called Wearable Code. It is based on an Adafruit Gemma wearable computer and a NeoPixel digital LED. An Arduino sketch running on the Gemma blinks a customizable message in morse code. You can decide which of the many uses of codes it represents.
The core of this project is the Gemma and NeoPixel. Everything else can be easily improvised. You can make the wearable pin rather than hang. You can use completely different materials. You can change the power from button batteries to a rechargable LiPo battery. If you are willing to change the Arduino sketch (another type of code), you can even use a different microprocessor and LED.
But, that's all for you to decide. This instructable will show you one way to build it as a starting point.
Here's a list of materials used (see photo):
And, a list of tools (see photo):