He could have run a wire up through the house walls to an LED indicator but decided to go wireless with a 433mhz transmitter. There is a second Arduino inside equipped with a 433mhz receiver.

But thanks to the rtl_433_ESP Arduino library developed by [NorthernMan54], we’re now able to pack that functionality into a much smaller package. All you need is an ESP32 microcontroller and a ...

Together with the Arduino code you will require as well as schematic’s and part lists allow you to create your very own one-handed Arduino powered quad copter transmitter.