Found this ESP32-C3 smartwatch (basically just comes with a demo installed) on Aliexpress for 19 euros.

Decided I wanted a temperature monitor in the case, so I put together some ESP-IDF plus LVGL code. It scrolls through different sensor data (customizable, mine has water/CPU/GPU temperature and CPU/GPU power consumption) which it pulls from the PC’s LibreHardwareMonitor web server via Wifi.