Here is a list of projects that you can do with an Arduino that are fun ... an accelerometer for detecting motion, or a Piezo ...

Sometimes, a project ... using an Arduino and sensors on the hardware side, and a Python front end for data visualization. It’s even complete with 3D printed enclosure and sensor elements.

[Edward], creator of the Cave Pearl project ... sensor on the I2C bus — these sensors are cheap and readily available. This isn’t about connecting a temperature sensor in your Arduino.