Temple explained: Deepinder Goyal's bet on wearables to extend healthy life

Temple, the wearable from Deepinder Goyal, is set to enter the market soon with a pill shaped design that tracks brain blood flow and monitors changes in real time in attempt to extend healthy life

Zomato and Eternal founder Deepinder Goyal’s Temple fitness device is nearing its commercial launch, with pre-orders for the limited-edition wearable expected to open soon and shipments planned before the end of 2026. Unlike regular fitness trackers worn on the wrist or fingers, Temple sits on the side of the head and is designed to continuously track blood flow to the brain.  

 

Goyal says the device measures what Temple calls Brain Flow, a proxy for cerebral blood flow and is focused at showing how factors such as exercise, sleep and meditation affect it. The idea is linked to his “Gravity Ageing Hypothesis”, which explores whether the effects of gravity on blood circulation could play a role in ageing and cognitive decline.  

 

 

What is a Temple

 

Temple is a wearable developed by Temple Private Limited, founded by Goyal. The device is worn on the side of the head, near the temple. According to Goyal, the device continuously monitors blood flow to the brain. The objective is to make a measurement that has traditionally required clinical equipment available through a wearable that can be used during everyday activities.  

 

Goyal has described Brain Flow as a proxy for cerebral blood flow, or the movement of blood through the brain. He says this measurement can respond to several activities and conditions, including aerobic exercise, cold exposure, meditation and sleep. It can also fall when a person sits for too long or becomes dehydrated.  

 

The idea is therefore, not simply to give users another number on a health dashboard. Temple is designed to show how the brain's blood-flow response changes as people go through their normal routines.

 

The device has also become smaller during development. Goyal said the latest version is less than half the size of earlier prototypes. He described it as the smallest wearable on the market by volume.

 

How does the wearable stay on the head

 

Temple uses single-use Grips, which are essentially tapes designed to hold the device against the skin. Goyal said the device comes with an unlimited supply of these Grips and that developing the right adhesive was itself a major part of the product development process.

 

According to him, the Grips are designed to keep Temple in place during running, jumping, swimming, showering and sauna use. The device has a battery life of around seven days. While Goyal said some people use a single Grip for roughly that long, the company recommends changing the Grip every two to three days.

 

The device can be removed, but a used Grip is not meant to be reused. Goyal has also said that users can continue normal activities such as face washing, showering, skincare and make-up while wearing Temple. He described the wearable as comfortable after an initial adjustment period of around five minutes. On itching, Goyal said he had not heard of users experiencing it so far. He attributed this to the medical-grade Grips used to hold Temple in place.

 

What is the Gravity Ageing Hypothesis?

 

The science behind Temple is linked to what Goyal calls the Gravity Ageing Hypothesis.

Humans spend much of their lives sitting or standing, which means gravity constantly pulls blood towards the lower parts of the body. The heart has to work against this force to move blood upwards towards the brain.

 

According to the hypothesis, this process continues over decades and could potentially affect brain function and contribute to ageing and cognitive decline. Temple is intended to measure this “struggle” by monitoring changes in blood flow to the brain.    

 

Why does Temple focus on brain blood flow?

 

Goyal says blood flow to the brain changes depending on what we do and what is happening in the body. For example, he says Brain Flow rises with aerobic exercise and cold exposure, while meditation and better sleep can also affect it. On the other hand, prolonged sitting and dehydration can cause it to fall.    

 

This makes cerebral blood flow potentially useful as a way of observing how the body responds to everyday habits. Goyal says that until now, measuring cerebral blood flow continuously during everyday life has generally not been possible with ordinary consumer wearables. Temple is intended to address that gap by providing a continuous reading rather than a single measurement taken in a clinical setting.  

 

Temple’s focus is based on the idea that blood flow to the brain is an important part of overall health. The company says the brain accounts for about 20 per cent of the body’s blood supply and argues that changes in brain blood flow could be relevant to ageing, sleep, recovery and other aspects of health. Temple’s pitch is that continuous tracking could provide information that is difficult to obtain through conventional clinical measurements.

 

Does Temple actually measure blood flow to the brain

 

This is one of the main questions about the Temple. Since the device sits on the head, it needs to show that its readings are coming from the brain and not just the scalp.

 

In its second validation study, Temple BrainFlow was compared with time-domain near-infrared spectroscopy (TD-NIRS), a method that can separate blood-flow changes in the brain from those in the scalp.  

 

The study involved 44 healthy young men across 60 sessions. They underwent three tests: a head-down tilt, a stand-to-squat movement and a stand-to-supine movement. Researchers then compared Temple's readings with the TD-NIRS measurements.  

 

According to results shared by Goyal, Temple's readings were more closely linked to blood flow in the brain than in the scalp. The correlation with brain blood volume ranged from 0.84 to 0.91. During the head-down tilt, the correlation was 0.91 for the brain, compared with 0.49 for the scalp.    

 

Temple was also tested against Transcranial Doppler

 

Temple's first validation study compared its BrainFlow readings with Transcranial Doppler (TCD), a method used to measure blood flow in the brain. The study involved 23 healthy adults who underwent cycling and a standing-to-supine movement. Goyal said that when participants lay down, their heart rate fell while brain blood flow increased, and Temple tracked the change alongside the Doppler.  

 

Across the two tests, Temple's BrainFlow showed a correlation of around 0.8 with Middle Cerebral Artery velocity. Goyal described this as an initial step, with the study posted as a preprint and further validation work still underway. 

 

What else does Temple measure

 

Brain Flow is not the only metric being developed for Temple. Temple also tracks a metric called Entropy, which Goyal describes as the body’s real-time “cost of being alive”.

 

According to him, the metric changes with factors such as sleep, stress, exercise, caffeine and meditation. The company is also working on Entropy, which Goyal describes as a new biomarker that measures the body's parasympathetic state. He said the metric has been observed to change in real time during meditation, even when heart rate remains stable.    

 

The metric is updated every second and is shown on an index ranging from 1 to 250, with lower numbers representing deeper rest, according to Goyal. He said the lowest levels have been recorded among fit, experienced meditators, while a score of 250 has been seen in elite athletes at the peak of their performance.

 

Explaining the idea, Goyal said that activities ranging from sleep and stress to sprinting, coffee and meditation affect the body’s metabolism and its cost of being alive. Entropy is designed to track these changes in real time.

 

Temple has also collaborated with the Sri Sri Institute for Advanced Research (SSIAR), the research arm of the Art of Living, to study how different meditation practices affect Entropy. Goyal said results from those studies will be published later.