When some years ago the Arduino Uno became popular, I had the idea to create a „bat detector shield“ for it. Together with Tony Messina I redesigned his „simple bat receiver“ so that it fits on a shield together with some pushbuttons and LEDs as user interface:
Tony created this page about the Ardubat: http://batdetector.freevar.com/ArduBat/
Tony even made a „Wifi-Ardubat“ with a built-in webserver. First he hade his own board, but then ESP8266 boards in the size of an Uno board became available. Here is this project: http://batdetector.freevar.com/ArduBat/WiFiBat.html
There are still a few kits (boards and all components) and some extra boards left, but the DHL shipping prices have gone up and the regulations require now sending goods in boxes (while a board would fit in an enveloped), so unfortunately international shipping has become complicated and expensive.