If you're worried about your home's safety and want to discourage possible thieves, the Vesta magnetized alarm for doors and windows is what you need. You just have to attach the alarm and the magnet to a door or a window, and turn it on when there is no one at home. If the door or window is opened, the magnet and the alarm will separate making the alarm ring.
It features an alarm button with siren, bell, and muted modes. The alarm will sound for approx. 15 seconds, and it will activate again after 30 seconds if the window or door remains open. It includes 1 double-sided sticker to attach the alarm (approx.: 5 x 10.5 x 0.5 cm), and 1 magnet (approx. 1 x 3 x 0.5 cm) with double-sided sticker. Battery operated (2 x CR2032).