With only an arduino board, two servos, and an hc-sr04, and some python, you can create a room scanner that is capable of showing depth!

Build a simple incident light meter for old meterless film cameras

Monitoring temperature and humidity without using a WiFi connection. Suitable for a chicken coop.

An Arduino-based digital scale with HX711 and VFD display.

FSM that allows to identify the direction of the object.