Create a simple application using digital or analog input and digital output.
I explored different sensors that use digital or analog input and output. First one was using "Force sensitive resistor(FSR)". It detects physical pressure, squeezing and weight.
Then I used "Ultrasonic range sensor". Ultrasonic Module has 4 pins (Ground, Vcc, Trig, Echo).
Finally, I created a digital input and output circuit using buzz sensor, ultrasonic range sensor and 8ohm speaker. There are 6 LEDs, each has a different note from C to G. When you move your hands, the value of distance would change and LED would light up according to the distance.