During the last year of high school, we had to form a team for a project that would last 6 months. This time we had to find and choose a subject. One person from the team was doing floor work in his house, and had the idea to build a machine that would scan for wall irregularities, and then draw it on the piece of floor that would later be against the wall so the worker could cut the piece according to the wall.
The image above is an unfinished prototype we took during the process of the actual making. It's missing the boards and the sensor.

The machine was working with an arduino board, an ultrasound sensor, a stepper motor, a belt, a battery, and incremental coder, and a pen holder assembly. I was, with another person from my team, in charge of programming the Arduino board. We wrote a program that would work without any button or anything. The first step was the scanning process. We had to move the sensor before the irregular wall for it to be scanned. A small wheel was helping us for that. While moving, the incremental coder was measuring the distance, so the pen could trace the exact distance once the scanning was done. Then, we would put the machine on the piece of floor, and thanks to the belt, stepper motor and pen assembly, it would draw the line for us to cut.