To get the tones from speaker to the Arduino, he hacked the Bluetooth speaker’s circuit board, redirecting its output to an Arduino analog pin.

Now the goal is the same but he has an even more surprising plan, throw the ADC out entirely and sample an analog thermistor using digital IO.

While a Raspberry Pi is a full-fledged computer that can do more complex things than an Arduino microcontroller, it's not the best choice for every project.