Sploony is firmware that lets ESP32 SoC boards interact with the Lightning Network. One or multiple Sploonies can connect directly to a single lnd to display machine-readable invoices, and act upon its invoice once paid. See a video of it here: https://twitter.com/sakak_musdom/status/1084857547947880448

The ESP32 platform is the cheapest hardware capable of practical secure connection to lnd, many of which form the cheapest practical payments network. A board from Aliexpress costs US$7 plus shipping. This combo enables many new business use-cases: micro-Point of Sales, sub-cent vending machines, public lockboxes, charging stations etc.

If you have an lnd node with a publicly reachable REST gateway, and an ESP32 development board, you can compile and run Sploony using PlatformIO or Arduino IDE. A quick guide can be found here.

• Fetches invoice from lnd and monitors its payment status
• Generates QR code in device and displays on OLED screen. QR on 0.96" OLED displays readable with most modern phones.
• Persists last invoice in SPI flash memory, and checks invoice status on powerup.
• TLS secured connection to your own lnd
• Uses readonly and invoice macaroons, which won't compromise your funds if leaked.

• Check invoice expiry!!!
• Captive portal for WiFi and LN host config
• Connect to BTCPayServer
• Better modularity to support different peripherals: bigger TFT displays, Neopixel LEDs, keypad input etc.
• Fleet management web UI

• Also check out https://github.com/arcbtc/1.21 if you're working with Acinq Strike