ESP-01S WiFi Serial Transceiver Module (ESP8266) | The Pi Hut
GitHub - har-in-air/ESP8266_BLUETOOTH_AUDIO_VARIO: A bluetooth audio vario with zero-lag climb/sink rate feedback. Configurable and firmware upgradable via WiFi. Uses off-the-shelf modules. Schematic and PCB layout provided.
Build Arduino Bluetooth Speaker with Reactive NeoPixel LEDs