Ispired by
this project, I made my version (it supports LCD display), using Arduino Nano board's ADC. Result (calibrated with accurate SG) on input level is sent via serial interface (USB), and it is displayed on 2 rows LCD (with I2C interface).
Since this is essentially broadband rectifier/log amplifier, it will record only signal level in the whole receiver band (determined by BPF), but it could still be useful.
If anyone is interested, I can post more details of my design.