A mostly 3D printed "renishaw" style touch probe. Complete design and construction details here: http://tomhorsley.com/hardware/solidoodle/solidoodle-renishaw.html
I have no idea how well it works since I still need to come up with a probe to attach and interface it with my printer.
This uses all the ideas from thing 94169, but all the parts are 3D printed.
Update: The aluminum binding posts were a mistake. Aluminum oxidizes too easily, a few days after I buff them up to make good contact, it starts having problems again. I need to find something else to use and rebuild the center part with different posts.
I've now uploaded a new version with the alt_ball part to use instead of the old post_ball. The alt_ball has a smaller hole to hold a piece of heavy duty bare copper ground wire. The copper seems to work much better than the aluminum binding posts.