Stärke

The Stärke (強 (ゲージ), sutraku; German for "Gauge", Japanese for "Energy/Strength Indicator") is a special instrument invented and implemented by the Vandenreich.

Overview
It is a tool which takes the appearance of a semi-transparent colored rectangular monocle that covers the left or right eye. In the most simplest sense, the Stärke is used to calculate the Kaliber (口径 (キャリバー), German for "Caliber", Japanese for "Power Level") of an opponent. It scans the level of reiatsu from an opponent(s) that enter its range and converts the readings into numbers that allow the Quincy to properly gauge an opponent's capabilities. The reading will increase in proportional accordance with the concentration of active reiryoku (or in other words, reiatsu) that is focused through the target. Because of this, it does not track latent reiryoku, meaning a target may be capable of hiding a significant portion of their power. However, it is also possible to use the device to read the Kaliber levels of a technique as well (such as Kidō). For strategical purposes, the Stärke can provide actual location and bearings of a specific reading for a rather considerable distance. A clock is also programmed into the device.

It appears that the Stärke also serves the dual purpose of a communicator between devices, even if the two Stärke in question are dimensions apart.

Behind the Scenes
This was inspired by the Scouter tool used in Dragon Ball Z.