A 21-YEAR-OLD CHINESE DEVELOPER BUILT A REAL-TIME MAC PERFORMANCE MONITOR ON A DEVICE SMALLER THAN HIS PALM AND IT FITS IN A POCKET M5Stack CardPuter ADV - a credit card with a keyboard and color display that connects to a MacBook via BLE and shows CPU cores, RAM pressure, uptime and battery in real time while a Python server scans the device in the background. He wrote the entire BLE stack from scratch, debugged the asyncio event loop and launched a custom monitor server that streams system metrics directly to a tiny screen - and the whole thing fits in a jeans pocket. Mac performance monitors cost $30-80 on the App Store and show the same data in a browser window - he built a hardware version that works with no internet, no subscription and no open laptop. Built it for himself and released the code for free.