Door & Window Alarm

Two pieces, ten seconds, no tools and nothing left on the paint. From then on, nothing opens that door or window without a 120-decibel siren announcing it, and you are awake before anyone is more than a step inside.

No app. No wifi. No pairing, no hub, no account to make. A magnet, a battery and a siren, which is precisely why it still works when the hotel wifi doesn't. Switch it to chime and it becomes a doorbell instead: useful on a share-house room, a hostel locker, a rental's back slider.

Comes as a pair. Most rooms have more than one way in.