Inspired by the leveling system of his CNC, [Chuck] built a little circuit board to line up his 3D printer and he shares the details in the video you can see below. The idea is simple, the nozzle presses on the circuit board, which has a tact switch underneath. When the switch is closed, an LED lights up.
In practice, you measure the height of the board and use that for your Z offset and you are done. Our only concern would be how repeatable the switch is. Granted, most people use a piece of paper, and that probably isn’t completely repeatable or accurate either. Correct feeler gauges are the “right” way to go, but we know few people who do that.
If you ever look at the repeatability of different Z-buttons like the proximity sensors or the little pins falling out of a 3D touch probe, they are not that repeatable. Some people also use microswitches, which is pretty similar to this approach and seems good enough.
The board is available, but it’s simple enough that you can make it – or its equivalent – using just about any method you use with your PCBs. [Chuck’s] Prototype board was milled. We are always surprised that more people are not using the nozzle themselves to feel the bed. Some people even go to a lot more trouble with CNC than just making electrical contact.