An outdoor camera films and records, but you have to open an app to find out. A standalone motion alarm does the opposite: it keeps no images, but it sounds immediately, with no connection and no phone needed.
What it does that a camera does not
A connected outdoor camera depends on a WiFi network, an open app or a notification read in time. A wireless motion alarm needs none of these: it sounds on the spot, the very moment movement is detected within its range, whether or not anyone is looking at their phone. It mounts on its adjustable bracket, protected from rain by a small roof, with no WiFi or app required.
What no study can confirm
We must be honest on one specific point: no official French study specifically measures the deterrent effect of a standalone motion alarm, independently of a camera. Existing work on visual deterrence, such as the meta-analysis by Piza, Welsh, Farrington and Thomas published in 2019 in Criminology & Public Policy, covers video surveillance, not an audible alarm alone. The principle of deterrence by surprise, an unexpected signal that increases the perceived risk of being spotted, remains plausible by analogy, but it is not a conclusion validated specifically for this type of product, and it is better to say so clearly than to suggest otherwise.
A signal, not proof
Like a dummy camera, this alarm relies on surprise rather than evidence. It films nothing, records nothing and sends no remote notification. If no one is within earshot when it goes off, the alert is lost. It is designed to signal a presence to someone who is at home, not to monitor an empty home remotely.
Where to place it
Its flexible installation makes it a natural complement to a fixed camera: where the camera covers a specific angle, the alarm can be moved with the seasons, placed temporarily near a secondary access point, a garage, a side path, a low fence, or even indoors to watch a rarely used room.
The matching product
The Wireless Motion Detector Alarm sets off a 105 dB siren as soon as someone is detected within its 110° field. You arm and disarm it with its two remote controls, with no WiFi or app. The rest of the range is in the SentinHome catalogue.
Further reading
To cover the perimeter with images as well as sound, see the outdoor camera. And before a long absence, the French police's Opération Tranquillité Vacances.