Thinking about high side current monitors, there's one variant that uses a three-terminal device (ZXCT1009F is one example) of which terminals 2 and 3 are across the current sense resistor, and terminal 1 spits out a metered current.
That means that voltage across terminals 2 and 3 is proportional to current out terminal 1. When properly biased, this is the familiar property of transconductance.
Or, transresistance; it's a transistor. That ZXCT1009F is a zero V_be PNP transistor equivalent. What other interesting things can one do with such a gizmo?