On the subject of small DMMs, this is the Pantec in the middle, with battery to scale.
This is something like 20 years old. All it does is AC/DC volts, ohms and continuity beep, which is all you need on the sort of job where you didn't expect to need to take a meter with you - basic things like checking batteries, fuses, continuity and that there is power.
Below is the nearest equivalent contemporary unit I could find. Much bigger and chunkier. OK it 'feels' nice but I'd rather it was smaller.
A nice addition is a non-contact voltage detector, and a tip that retracts by turning the nose. It also has diode test.
A really dumb feature is you need a PZ0 screwdriver to replace the battery - for a tool designed for on-the-move use, this is just plain dumb.
An issue with the Pantec is it uses LR44 buttons.
I just can't understand why someone hasn't made a modern equivalent with improved funcitonality.
It doesn't need to be super accurate - an MCU with 10 bit ADC would probably be fine.