Radar or camera: what each one sees, and where each one can’t go

Two ways a room can notice a fall when nothing is worn. One makes pictures. One measures movement. Here is what that means for her privacy, and what neither of them can promise.

Written by the Liacare team · Sources checked Sept. 21, 2026 · 4 sources, linked below · Not yet reviewed by a clinician · How we check facts

Why this choice comes up at all

Most families start with something she wears: a pendant, a wristband, a watch. The trouble is the hours when it comes off. In a 2026 survey of 909 U.S. adults 65 and older, 64% of people who own a medical alert device said they don't wear it in the shower, and only 18% wear or carry it at all times.⁴

So families look for something that lives in the room. AARP's guide to alert systems calls this passive fall detection: radar or infrared sensors, on a wall or ceiling, that work without anything to wear.² Cameras with fall-detection software are the other route.

What a camera sees

A camera sees what you would see standing in the doorway. That is its strength. When an alert comes, a person can look and know at once whether it is real.

It is also the whole problem. To notice a fall, software has to watch the picture all the time, even in products that only save a clip when something happens. For many parents that is the end of the conversation. And the rooms that matter most are the ones where a camera is least welcome. Among falls that sent people 65 and older to the emergency room, about four in five happened at home, most often in the bedroom, the bathroom and on the stairs.³

What a radar sensor measures

A radar sensor sends out low-power radio waves and listens to what comes back. What it gets is not a picture. Researchers who reviewed 74 papers on radar fall detection describe the data as patterns of distance, speed and direction of movement.¹ There is no lens. It cannot show what she is wearing, what she is reading, or her face.

An illustration, not a recording. One common form of radar data is a point cloud: each dot is a reflection with a distance and a speed. The voice check at the end is how the device we are building works; other products differ.

Radio waves also pass through shower steam, where a camera sees fog. That is one reason radar sensors are so often sold for bathrooms.

What radar cannot do

• It has less proof behind it. The same review found that most radar studies rely on simulated falls, often acted out in a lab, and its authors ask for test participants of all ages.¹ Ask any vendor how the product has performed in real homes.
• It covers a room, not a house. Walls and solid doors block or weaken the signal. A sensor in the hallway will not watch the bathroom.
• It cannot show you what happened. You get an alert, not a view. Some products add a voice check for that reason: the device asks if she is all right before anyone is called.
• It is still data about her. No images does not mean no information. A sensor knows when she is in the room and how she moves. Ask what leaves the house, where it is kept, and who can see it.

Side by side

Whichever you choose, tell her

A device she does not know about is a betrayal, whatever is inside it. In many places recording someone without consent is also against the law. Show her the device. Explain what it can and cannot see. Let her say no, and let her switch it off. A safety net she agreed to will still be on the wall in a year.