From previous experience, NOT using a NANO, but trying to use an Arduino Mega now.
Some also suggested teensy, but those are a bit expensive.
An Arduino Mega based portable device, having portable power, a display and circuitry to measure voltage, current, pulses, test components (Resistors, Capacitors, Transistors and more) and also be able to serve as a Serial Terminal and MORE.
Handheld form factor
Input Push Buttons
Nokia Graphics LCD
Voltage Input - 0 to 50V or possibly
Current Input - 0 to 5A
Sqaure Wave Generator
Component Tester - a variant of the SemiConductor Tester
Battery Powered - Chargeable via USB
Serial Connection with PC