Last week, I've been working on adding a vu-meter to my ESP32 audio recorder. Its update rate is slow as I am not using sliding window averaging. I will try to fix that some time soon.
I also added a lock switch like you find in iPods. It works great.
I will also consider implementing double buffering for the OLED display so that I can avoid pushing the whole framebuffer on the I2C bus.
Now for the hardware part: I am currently on working a PCB prototype. It won't be much portable but it will help me on testing components that I plan to integrate.
I bought some TLV320AIC3106 audio CODECs to replace the PCM1808 my prototype currently has. Its main avantages are: no 5V supply requirements (great for battery operated devices!), a built-in microphone preamp and an audio output (useful for headphone audio preview).
I hope to publish another update log before the end of the month!