For the front sensors you need to be able to switch them off. The rear sensors are activated when reverse is engaged but the fronts will be live all the time, that means they will bleep at everything around them, including people walking in front, stopping behind another vehicle, even passing parked cars, that can drive you nuts so you need to be able to turn them off. The switches are readily available, you can find them easily on eBay and they have the park assist image on them.