The Owon B35 series of multimeters use Bluetooth Low Energy (BLE) to transmit readings to remote monitors. This ESP32  captures measurement data and displays it. It automatically recognize hold, min, max and delta buttons and also has indicator for low battery.

For this clock I used ESP32 and 2.4" LCD 320x240 display. Unfortunately I didn't pay enough attention to understand that "SPI" in product title was not about display but about SD card and display has parallel 8 bit bus. It delayed development for two days before I understood how to program it. To reduce memory consumption and eliminate flickering, numbers are drawn in virtual monochrome screen and then this screen is reflected on real screen. I use my own graphical library, it currently supports some SPI, I2C and now parallel 8 bit bus displays. The clocks starts, shows current time, connects to WiFi, synchronizes time with SNTP servers.
This is next step from my first experiment: https://github.com/jef-sure/digits_morping_dgx/blob/main/bezier-1-2.cpp