As a semi-professional plane spotter when I hear or see an aircraft fly over I will sometimes point at it. But I can't always tell if there's an aircraft flying over, and I can't be awake 24/7 so I miss some, which I find unacceptable.
Enter the auto spotter, a robot that is capable of pointing at the nearest aircraft continuously.
The auto spotter uses 1090Mhz ADS-B Out transmissions to work out where the nearest aircraft is relative to its location and works out the bearing and elevation for a pointer. This is the same public data that is used to feed flight information services and can be received by anyone with the right (relatively cheap) equipment; all commercial and many general aviation aircraft around the world use it to transmit their positions, speeds, altitudes and more.
You may have seen the pointer at EMF2022 (in between rain showers) and this talk goes into some of the details of how it was developed, and how it works.