A few years back we made a gauge for measuring large bores in hydraulic cylinders. Seems the company that bought it from us needed the software for it again. I had to dig through my old source code and see if I had a recent version, turns out I did. On this project I did the electronics, software and commissioned it.
What the device does is, you place it in the bore, set your zeros and then measure the bore all the way down. This way you can see if there are any high spots, low spots or waviness. The software keeps track of the position as well and provides a csv file of the data and plots it on the screen.
This was a pretty fun project, I might redesign it and make a more substantial attempt at monetizing it later.