Not really related to the book, but it's only yesterday that I've found out about AirplaneJS [0]. It picks up ADS-B radio signals from airplanes and display them over maps on browser like a local Flightradar. It's nice that you can interact with SDR in Node.js
About this book, it's interesting to see that there are more advanced applications of SDR on Chapter 13.
Do you, HN-friends, know any other toy/simple or advanced applications of SDR?