Electronic Mosquito Repellent Without having to apply harmful chemicals or sprays to Baby's delicate skin, this device is a safe and easy way to keep mosquitoes away from your baby. Hardly audible to humans, but loud and clear to mosquitoes, this device imitates the sound of a dragonfly's wing beat - the mosquito's mortal enemy. Can clip to pushchairs, playpens, carriers, car seats and more! Very popular for travel! Requires one 9 Volt battery (not included).