Anyone who knows what kind of measurement tool this is and what principle it uses?

well, from just a bit of research, its a wireless induction ammeter. for testing electrical validity of tiny surface mount parts. I imagine its specific to one type of component, such as inductors, and not general purpose. it would work by passing a controlled, stable microcurrent along its bridgewire, and measuring how much interference or flyback is generated. SMD inductors have a predictable design and method of operation, so its probably straightforward to detect their correct operation by induction. it may need the circuit to be powered or active, it may not, cant tell.