Is there a floating-ruler app for macOS?

I've used Free Ruler for Mac OS X in the past. I'm amazed that still works just fine. However, it does not allow click-through.

iconfactory's xScope

Powerful on-screen rulers for precise pixel measurements that include scaling, rotation, and edge snapping.

xScope’s rulers can be used to measure any on-screen element, including the distance and angles between objects. Holding down the Control key while dragging the ruler near an on-screen object causes the edges and ends of the ruler to “snap” into place, making measuring quick and easy. Additionally, the Ruler tool includes calipers which can be toggled on or off and used for outside measurements.

Not sure if non-pixel measurements are possible.