This Raspberry Pi-powered friend notification sign will seriously take your Minecraft server up a notch! The project was created from the ground up by a developer known as Wes from Geeksmithing on YouTube.
The sign relies on a Raspberry Pi Zero W, so you don't need anything big like a full-sized Pi. But you definitely need the Pi Zero W edition for its Wi-Fi support to get real-time updates.
When the Pi detects a friend has logged onto the server, a letter in the sign will illuminate. The LEDs are RGB and can be programmed with custom effects.
The case was built entirely by hand to spec by Wes. The lighting system is comprised of 49 Adafruit NeoPixel lights, carefully arranged behind each letter. When the lights are illuminated, the light is diffused behind a sheet of white acrylic.
If you want to examine the code behind the project, you're in luck. Wes shared everything used to drive the sign on Github. You can use this to recreate a similar project of your own.