I was curious to measure the power drawn by the many gadgets and laptops that charged over USB-C in our home. Looking for a suitable USB-C power meter, I chose Plugable USB-C VAMeter3.
This meter does full USB data passthrough while displaying the power consumed. It only touches the power (VBUS) and ground wires and leaves the rest undisturbed.
It can measure power drawn in either direction, so supports both devices sucking power and providing power. The arrow on the display shows the direction of electrical current.