Tangential, but what other fascinating things can I do with an SDR dongle? I've had one for years and have not heard of this.
* Listen to various radio stations
* Track airplane positions
* Receive weather images from a satellite
what else?
One other thing off the top of my head is combining ship position and cargo databases: https://github.com/marcdacosta/ambient-shipping
You can read TPMS sensors in car tires, wireless weather stations and much more, see this app: https://github.com/merbanan/rtl_433 for more examples.