The wearable health market has a dropout problem. About a third of people who buy a fitness tracker stop wearing it within six months, according to a 2019 survey by Gartner. The reasons are predictable: the band irritates their skin, they forget to charge it, or they just get tired of having something strapped to their wrist. Watches and rings and patches assume you'll tolerate a device on your body indefinitely. Many people won't.
This is why the next wave of health monitoring technology is moving in the opposite direction. Instead of making wearables smaller or more comfortable, researchers and companies are asking a different question: what if you didn't have to wear anything at all?
The answer is taking shape across several environments where people already spend their time — bathrooms, cars, bedrooms, living rooms. Sensors embedded in mirrors, toilets, car cabins, and room walls are beginning to capture vital signs passively, without the user doing anything differently. And camera-based systems using remote photoplethysmography (rPPG) can extract heart rate from a standard video of someone's face.
"Ambient diagnostics is a hard pivot from sick care to true health assurance, where the walls quietly track the signals long before symptoms show up." — IT Business Today, "Ambient Diagnostics 2026" (2026)
The bathroom becomes a lab
The bathroom is one of the few places where people follow a consistent daily routine. Stanford researchers recognized this over 15 years ago and started developing a smart toilet platform. The idea — analyze what the body produces every day, without any effort from the user.
In 2020, Seung-min Park and colleagues at Stanford published their system in Nature Biomedical Engineering. The toilet uses sensors to analyze urine flow rate, urine composition through test strips, and stool characteristics through computer vision. A pilot study of 21 participants showed the system could track individual health markers over time, catching early signs of conditions like urinary tract infections and irritable bowel syndrome (Park et al., 2020).
The concept earned an Ig Nobel Prize in 2023, which tends to happen when research is simultaneously funny and genuinely useful. But the underlying technology is serious. Continuous, passive monitoring of metabolic and gastrointestinal health through a device people already use multiple times a day solves the compliance problem that wearables can't. Nobody forgets to use the toilet.
Smart mirrors represent another bathroom-based approach. Companies are integrating cameras and sensors into bathroom mirrors that can measure heart rate, skin condition, and even estimate stress levels during the few minutes someone spends in front of the mirror each morning. The smart mirror health monitoring market saw rapid growth through 2024, with systems adding features like real-time coaching and integration with electronic health records.
Your car already watches you
In-car health monitoring is further along than most people realize. The market reached $2.4 billion in 2024 and is projected to hit $11.1 billion by 2034, growing at 15.4% annually (GM Insights, 2025). The primary driver is regulatory: the European Union's General Safety Regulation requires driver monitoring systems in all new vehicles sold after July 2024.
Most current systems focus on drowsiness and distraction detection using cabin-facing cameras. But the technology is expanding. Infineon's 60 GHz radar sensor, designed for overhead mounting in vehicle cabins, can detect breathing patterns, heart rate, and occupant presence — including detecting children or pets left in hot cars with 99% reliability (Infineon, 2025). Companies like Bosch, Continental, and Vayyar are building similar in-cabin sensing platforms.
The transition from safety monitoring to health monitoring is a short step. A car that already tracks your breathing rate and heart rate for drowsiness detection can flag irregular patterns that might indicate a health issue. You spend an average of 51 minutes per day in a car in the United States. That's 51 minutes of passive vital sign data that currently goes uncollected.
Ambient room monitoring with radar and sensors
Smart Meter launched iAmbientHealth in September 2025, a contactless remote patient monitoring system that uses radar and environmental sensors to track vital signs without any wearable device. The system mounts in a patient's room and continuously monitors respiratory rate, heart rate, sleep patterns, and room conditions like temperature and humidity.
This approach is particularly relevant for elderly patients and people with cognitive impairments who may not be able to manage wearable devices. A sensor mounted on the wall doesn't need charging, can't be lost, and doesn't require any interaction. It just collects data.
The technology relies primarily on millimeter-wave radar, which can detect the subtle chest movements associated with breathing and heartbeat through clothing and even bedding. Several research groups have demonstrated radar-based vital sign monitoring through walls, though clinical-grade accuracy in uncontrolled home environments remains an active area of research.
rPPG: vital signs from a camera
Remote photoplethysmography sits at the intersection of all these approaches. Where smart toilets need plumbing integration and radar sensors need dedicated hardware, rPPG works with any standard camera — the one in your laptop, your phone, your bathroom mirror, or your car's cabin-facing sensor.
The principle is straightforward. Each heartbeat pushes blood through capillaries beneath the skin, causing microscopic color changes invisible to the naked eye but detectable by a camera. Algorithms process these pixel-level color shifts to extract pulse rate, and more recent work has extended the approach to respiratory rate, blood pressure estimation, and oxygen saturation.
Clinical validation has advanced considerably. A 2025 study published in PMC analyzed 817 samples and found rPPG-derived pulse rate showed strong agreement with ECG, with a mean absolute error of 1.061 bpm, root-mean-squared error of 2.845 bpm, and Pearson correlation of 0.962 (PMC, 2025). A separate review in Nature Digital Medicine confirmed that forehead and cheek regions provide the most reliable signal for heart rate estimation.
The accuracy isn't uniform across all conditions. Darker skin tones absorb more light, reducing signal strength. Harsh or variable lighting introduces noise. Movement — even talking or chewing — creates artifacts. These are known problems with active research solutions, including multi-wavelength analysis, deep learning models trained on diverse datasets, and motion compensation algorithms.
How passive monitoring approaches compare
| Approach | What it measures | Where it works | Hardware needed | User effort | Clinical validation stage |
|---|---|---|---|---|---|
| Smart toilet | Urine composition, stool analysis, flow rate | Bathroom | Modified toilet seat/bowl | None | Pilot studies (21 participants) |
| Smart mirror | Heart rate, skin condition, stress indicators | Bathroom | Mirror with embedded camera | Stand in front of mirror | Early commercial, limited clinical data |
| In-car radar/camera | Heart rate, respiratory rate, drowsiness | Vehicle cabin | Cabin-facing sensors (often factory-installed) | None | Production vehicles shipping |
| Ambient room radar | Respiratory rate, heart rate, sleep patterns | Bedroom, living room | Wall/ceiling-mounted radar unit | None | Early commercial (iAmbientHealth launched 2025) |
| rPPG camera-based | Heart rate, respiratory rate, blood pressure (experimental) | Anywhere with a camera | Standard camera (phone, laptop, dedicated) | Face visible to camera for 30-60 seconds | Clinical validation with MAE of 1.06 bpm for HR |
Sources: Park et al. (2020), GM Insights (2025), Infineon (2025), Smart Meter (2025), PMC clinical validation (2025).
The table shows a clear pattern: different technologies fit different moments in the day. No single approach covers everything, but layered together, they could create nearly continuous passive monitoring — bathroom in the morning, car during the commute, ambient sensors at the office, rPPG during video calls, ambient radar while sleeping.
What actually needs to happen
The technology exists in various stages of readiness. The harder problems are regulatory, privacy, and integration.
Regulatory frameworks haven't caught up. The FDA has cleared some rPPG-based systems for specific measurements in adults, but there's no unified framework for ambient health monitoring devices. A smart toilet that detects potential kidney disease doesn't fit neatly into existing medical device categories. Regulators will need to develop new pathways that account for passive, continuous monitoring in non-clinical settings.
Privacy concerns are real and unresolved. A camera watching your face to measure heart rate is also a camera watching your face. Radar sensors that detect breathing through walls could theoretically monitor anyone in range. Smart toilets record data that most people consider deeply private. Any passive monitoring system will need robust data handling practices and clear user consent mechanisms to gain trust.
Interoperability barely exists. Your smart toilet doesn't talk to your car's health sensors, which don't talk to your bathroom mirror, which doesn't talk to your doctor's EHR system. Until these data streams can be integrated into a coherent health picture, the value of each individual system stays limited.
Circadify is developing contactless vital sign measurement technology using rPPG, designed to work with standard cameras across multiple settings. The company's research focuses on extracting heart rate, respiratory rate, and other physiological signals from facial video — an approach that could integrate with mirrors, vehicle cabins, telehealth platforms, and other environments where cameras already exist.
Frequently Asked Questions
What is passive health monitoring?
Passive health monitoring refers to systems that collect physiological data without requiring the user to wear a device or actively participate. Examples include cameras that measure heart rate from facial skin color changes, radar sensors that detect breathing patterns through walls, and smart toilets that analyze waste for disease markers. The goal is continuous health data without any change in daily routine.
How does rPPG measure vital signs without contact?
Remote photoplethysmography (rPPG) detects tiny changes in skin color caused by blood flow beneath the surface. A standard camera records facial video, and algorithms extract the pulse signal from those color fluctuations. Clinical validation studies have shown mean absolute errors as low as 1.06 bpm for heart rate compared to ECG, though accuracy depends on lighting, skin tone, and motion.
Are smart toilets a real health monitoring technology?
Yes. Stanford researchers led by Seung-min Park published a smart toilet system in Nature Biomedical Engineering in 2020 that analyzes urine flow, stool consistency, and molecular markers. A pilot study with 21 participants demonstrated the system could track health indicators over time. Several companies are now developing commercial versions.
When will wearable-free health monitoring be widely available?
Some components are already available. In-car driver monitoring systems are shipping in production vehicles, and ambient radar sensors are entering the remote patient monitoring market. Camera-based rPPG systems have received regulatory clearance for adult use in some markets. Widespread consumer adoption of integrated passive monitoring across multiple environments is likely still 5 to 10 years away.