What is Shubman Gill wearing on his forehead? The new wearable that aims to track the brain

Shubman Gill's appearance with a small device attached to the side of his forehead during India's practice session in Auckland has attracted attention beyond the cricket field. The Indian captain was spotted wearing the unusual gadget while preparing for the upcoming ODI series against New Zealand on October 29, 2026.

The device is called Temple. Unlike conventional fitness trackers that monitor steps, heart rate and sleep, it is designed to track physiological signals associated with cerebral blood flow and provide insights into the body's response to physical and mental demands.

Gill is not the first Indian sportsperson to experiment with it. Badminton star PV Sindhu was spotted wearing the same device during international competition earlier this year.

Developed by a team associated with Zomato co-founder Deepinder Goyal, Temple raises an interesting question about the future of sports science: could monitoring signals associated with the brain help athletes understand fatigue and recovery better than conventional fitness trackers?

However, there is an important distinction between what the device claims to measure and what has been scientifically established about its usefulness in professional sport.

What exactly is Temple?

Temple is a wearable health and performance-tracking device developed by a team associated with Deepinder Goyal, the founder of Zomato.

It is designed to sit on the side of the forehead, near the temple, and attaches to the skin using specially designed adhesive patches known as Grips.

Unlike a smartwatch, which primarily tracks conventional fitness parameters, Temple focuses on physiological signals associated with the brain.

The technology behind the device is called BrainFlow. It uses optical sensors to monitor changes in blood volume in the tissue around the temple, with the aim of tracking signals associated with cerebral blood flow.

Cerebral blood flow refers to the circulation of blood through the brain. It plays an important role in supplying the brain with oxygen and nutrients.

Temple uses photoplethysmography (PPG), an optical sensing technology that detects changes in blood volume using light. Its optical system uses different wavelengths, including green, red and infrared light.

However, Temple is not an EEG machine. It does not directly record electrical activity in the brain, read thoughts or measure intelligence. Instead, it generates a proprietary BrainFlow index intended to reflect relative changes in cerebral blood-flow-related signals.

What does the device actually measure?

Temple aims to go beyond the usual fitness measurements available through smartwatches and fitness bands.

Some of its key features include:

1. BrainFlow

One of its central features is the BrainFlow index, which tracks changes in optical signals associated with cerebral blood flow.

This could potentially help researchers study how the body responds to physical exertion, rest and other conditions.

However, the index should not be confused with a direct measurement of absolute blood flow inside the brain.

2. Cognitive workload

Cognitive workload refers to the mental effort required to perform a particular task.

In professional sport, this could involve concentration, decision-making, anticipation and processing information under pressure.

For a batter, reading a bowler's action, judging the length of a delivery and deciding whether to defend or attack require continuous mental processing.

Temple aims to provide additional physiological information that researchers may use to study these demands. It should not, however, be described as a device that directly measures concentration or reads thoughts.

3. Physical strain and recovery

Physical fatigue is not always reflected by how an athlete looks or feels. Training intensity, sleep, stress and recovery can influence the body's physiological responses.

Temple aims to provide additional information about these changes, potentially helping athletes and their support teams study training demands and recovery patterns.

4. Entropy score

Another feature is its Entropy score, a proprietary metric developed to represent physiological strain.

According to explanations attributed to Goyal, the score operates on a scale of 1 to 250. It can change with factors such as exercise, sleep, stress and caffeine consumption.

The intention is to give users another way of understanding how their bodies respond to different activities.

However, it is not an established medical measurement of fatigue, stress or neurological health.

Who wore Temple before Shubman Gill?

Gill is not the first Indian sportsperson to attract attention for wearing Temple.

Indian badminton star PV Sindhu was spotted using the device during the Thomas and Uber Cup in Denmark in April 2026. According to The Indian Express, she had been testing it during training for several weeks before wearing it in a competitive match for the first time.

She was subsequently spotted wearing it during the BWF World Championships in August.

Her appearance with the device generated curiosity because it was unusual to see a forehead-mounted health tracker during an elite sporting event.

Goyal has also demonstrated the device publicly while explaining its technology and intended applications.

Gill's appearance in Auckland on October 29 has now brought the device into the cricketing conversation.

However, neither Gill nor Sindhu has publicly provided a detailed explanation of how the readings are being incorporated into their respective training programmes. It would therefore be premature to claim that the device has already improved either athlete's performance.

Why could it interest professional cricketers?

Cricket is often discussed in terms of physical fitness, technical ability and match temperament. But the mental demands of the sport are equally significant.

A batter can spend several hours at the crease, constantly assessing the bowler, field placements, pitch conditions and changes in the match situation.

For a fast bowler, maintaining concentration while repeatedly delivering at high intensity is another challenge. Fielders also need to remain alert for extended periods, even when the ball is not coming towards them.

Traditional fitness trackers can provide information about heart rate, movement, sleep and physical activity. However, these measurements do not necessarily explain every aspect of an athlete's mental workload.

This is where Temple's proposed technology becomes interesting.

If its measurements prove reliable and useful, it could potentially give sports scientists another way to study how athletes respond to physical and cognitive demands.

For example, coaches could explore whether certain training sessions are associated with greater physiological strain, how athletes respond to different recovery routines and whether changes in workload correspond with other performance indicators.

But there is a difference between collecting data and establishing that the data can improve performance. Temple's actual value in elite cricket will depend on scientific validation and evidence that its insights can translate into better training decisions.

What does scientific research say about Temple?

Temple's claims have attracted scientific interest, but the available research also highlights why its technology needs further examination.

A study titled Concordance Between a Temple-Worn Optical Wearable and Transcranial Doppler During Exercise and Postural Transitions in Healthy Adults was published as a preprint on medRxiv in September 2026.

The researchers compared Temple's BrainFlow index with transcranial Doppler (TCD), an ultrasound technique used to measure blood-flow velocity in a major artery supplying the brain.

The study involved 23 healthy adults. Twenty participants were analysed in each of two protocols: cycling exercise and a change in body position from standing to lying down.

The researchers reported significant correlations between the BrainFlow index and the Doppler measurements, with median correlation values of 0.795 and 0.799 across the two protocols.

However, these findings need to be interpreted carefully.

The study examined how closely the two sets of readings followed changes over time. It did not establish that Temple could accurately measure absolute cerebral blood flow or that all its optical signals originated inside the brain.

There is another important detail: the study was funded by Temple Pvt Ltd. It was available as a preprint, meaning it had not yet completed peer review at the time of publication.

Therefore, while the findings offer an initial scientific basis for further investigation, they do not establish Temple as a clinically validated brain-monitoring device.

Can cricketers wear Temple while playing? What do ICC regulations say?

This is perhaps the most interesting question surrounding Gill's appearance with the device.

The International Cricket Council (ICC) has regulations governing electronic communication devices and the conduct of players within designated areas during international matches.

However, these regulations do not mean that every electronic health tracker is automatically prohibited.

1. Restrictions on electronic communication devices

The ICC's Player and Match Officials Area (PMOA) regulations prohibit communication devices within designated areas, subject to specific exceptions.

These areas include team dressing rooms, dug-outs, match-viewing areas and other designated spaces.

The rules are intended to prevent unauthorised communication and the disclosure of sensitive information during matches.

In May 2018, the ICC clarified that smartwatches connected to phones, Wi-Fi or capable of receiving communications would not be permitted on the field of play or in designated PMOA areas.

The distinction is important: a device that collects physiological information is not necessarily the same as a communication device.

2. Does the rule automatically apply to Temple?

Not necessarily.

Temple is designed primarily for physiological monitoring. However, its technical capabilities, including connectivity and communication functions, would need to be considered when assessing whether it falls under the relevant restrictions.

The ICC's published PMOA regulations do not specifically name Temple or expressly prohibit this device.

Consequently, it would be inaccurate to claim that Temple is either universally permitted or expressly banned during international cricket.

Its use during an official match would need to be assessed under the applicable ICC regulations, playing conditions and approval requirements.

Sindhu wearing Temple during a competitive badminton match does not establish that the device is automatically permitted in international cricket.

The fact that Gill wore it during a practice session also does not establish that he can wear it during an official match.

Relevant regulations are available through the ICC's official website:

• ICC Player and Match Officials Area regulations

• ICC Playing Conditions

When will Temple be available to the public?

Although Temple has already attracted attention through prominent Indian sportspersons, it is moving towards its first wider consumer rollout.

Goyal announced that pre-orders for the first batch would open on November 1, 2026.

However, there has been a subsequent development. On October 29, Goyal announced that pre-orders had already opened for people who had registered for early access.

Public pre-orders are scheduled to begin on November 1.

According to his announcement, each device will be made to order, with deliveries expected within three months of purchase.

The company has not yet disclosed the exact number of devices planned for its first batch.

The commercial launch will be an important step in determining whether the technology can move beyond demonstrations and limited testing by prominent athletes.

What are the limitations of Temple?

Despite the interest surrounding the device, its claims deserve careful examination.

Monitoring physiological signals associated with cerebral blood flow is considerably more complicated than measuring steps or heart rate.

Readings from optical sensors can be influenced by movement, sensor positioning, surrounding tissue and other physiological factors.

More importantly, detecting a change in a physiological signal does not automatically establish why that change occurred or what it means for an athlete's performance.

For example, a change in a reading does not necessarily indicate that a player is mentally exhausted or unable to concentrate.

The September 2026 preprint provides some initial evidence that Temple's BrainFlow index follows changes recorded through transcranial Doppler under specific conditions. However, further independent research is required to establish its cerebral specificity and practical applications.

For now, it should be viewed as an emerging wearable technology rather than a proven performance-enhancing tool or a medical diagnostic device.

The bigger picture: Is sports science moving beyond physical fitness?

Gill's appearance with Temple reflects a wider development in professional sport: the growing interest in understanding athletes beyond conventional physical fitness measurements.

For years, teams have invested in monitoring heart rates, workload, sleep patterns, muscle recovery and injury risks. Technology is now attempting to explore additional physiological indicators associated with cognitive demands and recovery.

This is particularly relevant in sports such as cricket, where physical endurance and mental concentration often need to work together for extended periods.

However, technology should complement an athlete's preparation, not replace coaching, medical supervision or established sports-science practices.

Temple has attracted attention because it attempts to explore an area that conventional fitness trackers largely overlook.

Whether it becomes a meaningful addition to professional cricket or remains an experimental wellness product is a question that further testing and scientific evidence will answer.

For now, Gill's forehead-mounted wearable has opened an interesting conversation about the future of athlete monitoring. The next big development in sports technology may not simply be about measuring how much an athlete runs or how fast they bowl, but understanding how their body responds to the demands placed on it.