This is a z-probe for delta printers (kossel, anycubic, micromake, 20x20... ). It is semi-automatic as mgx (https://www.thingiverse.com/mgx/about) defined it in the sense that you need to attach it to the extruder when in use, then remove it.
I found it this semi-automatic a a good solution although it was measuring on the side of the nozzle introducing some error. I redesigned considering this aspect and in this version (fish probe) it places itself under the nozzle, and it aligns almost perfectly to it. You just need to measure the z distance between the nozzle and the micro-switch to add to the height of the printer.