I used the sensor when my son was six. The theory was that he was supposed to awaken at the noise, stop peeing, and finish in the bathroom. It was supposed to train his body to recognize when the bladder was full. The reality was that although it sounds like a smoke detector going off, he could have slept through it. So, at the first sound, I lept out of bed, grabbed the sensor and wiped it to stop the noise (we had a baby in the other bedroom), woke my son and gave him a jar or took him to the bathroom, changed the underwear, and put him back to bed. The first week, the buzzer sounded about 3 times a night, it decreased to about twice, then once a night, and he stopped wetting around week six. He never ever woke in the night to use the bathroom, and peed a gallon every morning.
At age 5, 5% of all boys still night time wet, by age 6 it is 1% of boys. Some kids with a family history of nighttime enurisis wet until adolescence. I don't know why the buzzer worked for us. I gave it to several other of my patients and it didn't work for them and they weren't as dedicated at getting up as I was. The medication DDVLP works about 50% of the time to decrease the frequency of the wetting.
We tried no fluids after 6, and bathroom trips around midnight, but it didn't help. With the buzzer, I could see that he wet frequently all night.
Good luck and good night.