For my project I wanted to test to see if an Apple could utilize a capacitive sensor to trigger a threshold sense and send a signal to the arduino. I set up a capacitive sensor and connected the end of the sensor to the Apple. I then connected the LED I was going to use as a sensor indicator and then mapped it into the code, setting a threshold to trigger the LED when a strong enough signal was sensed by the capacitive sensor. The apple was very conductive and would react very strongly to even the smallest human touch. In this video, you can see how touching the apple will immediately turn the LED on and off.
Here is code that I used for the project. I used a threshold of 1000 to track the conductive sensing.