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Temple uses green, red and infrared light sensors to track optical signals linked to cerebral circulation.
Its BrainFlow index estimates relative changes in blood-flow-related signals rather than absolute brain blood flow.
Early research shows promise, but independent studies must confirm its accuracy and clinical value.
Temple has gone down a different road in the health wearable market. Instead of yet another smartwatch or fitness band, the company has built a small device that sits near the temple and tracks signals linked to blood flow in the brain.
The product, associated with entrepreneur Deepinder Goyal, promises a closer look at cerebral health using optical sensors. Its core technology, called BrainFlow, is what sets it apart from ordinary consumer wearables. Early research has sparked interest, but it has also raised real questions about accuracy.
Temple relies on photoplethysmography (PPG), an optical technique that picks up changes in blood volume using light. Smartwatches already use PPG to track heart rate at the wrist. Temple takes the same basic idea and moves it to the side of the head, near the temporal region.
The device shines green, red, and infrared light into the tissue near the temple. As blood volume changes, blood and the surrounding tissue absorb and reflect different amounts of light. Small sensors catch these shifts and collect the optical signals, and software then studies the patterns to produce a result called the BrainFlow index.
This index is meant to show relative changes in signals linked to cerebral circulation. It doesn’t directly measure blood flow across the whole brain, and it doesn’t give an absolute blood-flow value. That distinction is important when you’re weighing up the product’s health claims.
BrainFlow is the headline feature, but Temple also looks at other signals from the body. These include heart rate, pulse-wave patterns, perfusion-related features, and optical signals linked to hemoglobin. Each metric gives a different view of how the body responds to exercise, rest, posture, and other daily activity.
The BrainFlow index combines several optical features to estimate changes in cerebral hemodynamics, which is the term for blood flow and related forces inside the brain’s blood vessels. The result is a proprietary score, not a direct clinical measurement. So Temple is aiming to show useful trends, not hand out a medical diagnosis.
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A September 2026 preprint compared Temple with transcranial Doppler (TCD), an established ultrasound method that measures blood-flow velocity in the major arteries of the brain. The study involved 23 healthy adults, with 20 participants in each test protocol. Researchers recorded data from both devices during cycling exercise and while participants moved from standing to lying flat.
Temple’s BrainFlow output followed broad patterns that also showed up in the TCD readings. That’s a reason to keep researching, but it doesn’t prove the two methods measure the same thing. The small sample, the healthy participant group, and the preprint status all weaken the evidence.
A separate benchmark study compared Temple’s heart-rate results with five consumer devices and a Polar H10 chest strap. The comparison included the Apple Watch Series 12, Garmin FR970, Fitbit Air, WHOOP MG, and Oura Ring 5. Goyal reported an average error of about 1.14 beats per minute at peak exercise. Since this research was shared by the company, independent tests will need to confirm the claim.
Temple has a compact, pill-shaped design that rests near the side of the head. A medical-grade adhesive grip holds it in place, and the design is meant to fit under regular glasses. The company recommends swapping the grip every two to three days. The device is also built for continuous wear, with sleep as one of its planned use cases.
The reported launch range comes in six colours: True Gold, Rose Gold, Black Mirror, Real Jade, Deep Blue, and Purple Funk. Indian pre-orders opened on November 1, 2026, at a reported price of Rs. 85,000. Goyal also mentioned a 14-day no-questions-asked return policy for Indian buyers. Battery life, long-term comfort, and the full retail rollout are still key details that buyers will want to know.
The biggest worry is the gap between a signal near the skin and the complicated blood supply of the brain. Cerebral circulation involves many arteries and blood vessels, and each brain region has its own needs. A sensor at one spot on the head can’t automatically stand in for blood flow across the whole organ. Blood flow in the skin can also affect optical readings.
Medical experts have also challenged claims that tie BrainFlow to conditions like Alzheimer’s disease, cognitive decline, or faster brain ageing. A change in a circulation-related signal doesn’t prove someone has any of these conditions. The Gravity Ageing Hypothesis connected to Goyal’s wider research also lacks broad acceptance in the scientific community.
Why this Matters
Temple’s technology hints at a new direction for personal health monitoring. Most wearables track heart rate, sleep, and daily activity, while Temple is trying to study signals linked to blood flow in the brain. Better research in this area could help scientists understand cerebral health and build new tools for long-term health studies.
Temple could find a role in sports science, sleep research, aviation, and studies of age-related changes in cerebral circulation. Any of these uses depends on larger trials, peer-reviewed results, and independent tests across different ages, health conditions, and skin tones. Researchers also have to show that BrainFlow gives repeatable results over time and connects to meaningful health outcomes.
Temple brings a fresh idea to the wearable market, but its value depends on scientific proof, not its unusual design. The optical method has a clear basis, but using it as a measure of brain health still needs stronger evidence. At Rs. 85,000, the device is for now an experimental premium wearable, not a proven medical tool.
1. What is Temple's head-mounted wearable?
Temple is a health-monitoring device that sits near the temple and uses optical sensors to track signals linked to cerebral circulation and heart rate.
2. What is BrainFlow technology?
BrainFlow is Temple's proprietary system that processes optical sensor data to estimate relative changes in signals associated with blood flow in the brain.
3. How does Temple measure brain blood flow?
It uses photoplethysmography (PPG), which sends green, red and infrared light into tissue and detects changes in reflected light linked to blood volume.
4. How much does the Temple wearable cost in India?
The reported Indian pre-order price is Rs. 85,000. Pre-orders opened on November 1, 2026.
5. Can Temple detect brain diseases such as Alzheimer's?
No established clinical evidence confirms that Temple can diagnose Alzheimer's or other neurological diseases. Its BrainFlow technology still requires further scientific validation.