In old Taiwan, men were obliged to join the military when they reach age-20. Upon joining, each will be given a number. The numbers made it easy to keep track of the place and time you serve the army. For my finals, I sewed a random-numbered badge and connected each number as a digital input to Arduino, triggering the led.
One of my classmate told me that he actually has a military badge after I did my project.
For the future, I wish to create one that could read out the written number or name by using modular system.