Over on Reddit user olgierd has posted a video on this thread showing his work on developing a portable software defined radio based on an RTL-SDR R820T, the rtl_fm software and a Raspberry Pi with LCD screen. The software is based on rtl_fm which has the capability to demodulate FM/AM/SSB signals. His video shows him tuning to various signals using a tuning knob.
Note that his setup is capable of playing the audio, but it is not shown in the video as he only had earbuds connected. In the future he hopes to make it more portable by adding a li-ion battery.