There's a sensor that clips on to the crotch of the underwear. As soon as the sensor gets wet the alarm sounds and you have to physically disable it. It senses a very minute amount of wetness.
DD1 was 5 when we started it just prior to the start of kindergarten.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.