Deepinder Goyal’s Temple Takes First Step Towards Validating Its Wearable

Deepinder Goyal’s wearable startup Temple has released its first validation study, with researchers finding that its proprietary brain flow metric broadly tracked changes in cerebral blood-flow velocity recorded using transcranial Doppler (TCD) ultrasound. 

However, the study, published as a preprint, involved only 23 healthy adults and has been submitted for peer review.

TCD is a non-invasive ultrasound technique used to measure the speed and direction of blood flow in the brain’s major arteries. The study compared Temple’s metric with blood-flow velocity in the middle cerebral artery rather than directly measuring total or absolute cerebral blood flow. 

Researchers compared Temple’s wearable with TCD during two activities designed to produce changes in cerebral blood flow – stationary cycling and a shift from standing to lying down. Data from 20 participants was analysed under each protocol.

Temple’s brain flow metric registered a median within-subject correlation of about 0.8 with middle cerebral artery blood-flow velocity across both activities, according to the paper.

Goyal said in a post on X that the result demonstrated that Temple could track changes in brain blood flow that conventional heart-rate measurements might miss.

During the postural test, participants’ heart rates declined when they lay down, while cerebral blood-flow velocity increased. Temple’s metric moved in the same direction as the Doppler reading despite the opposing change in heart rate, the researchers found.

“Any device that only measures heart rate would have gotten this completely wrong,” Goyal said.

The findings suggest that Temple’s wearable can follow the direction and pattern of short-term changes in cerebral blood-flow velocity under controlled conditions. They do not establish that the device can accurately measure absolute cerebral blood flow or diagnose medical conditions. 

The paper also said further studies involving other measurement techniques and cerebrovascular challenges would be needed to determine whether Temple’s brain flow metric specifically reflects cerebral activity and to establish potential clinical applications.

Goyal acknowledged the limited scope of the research, saying it involved one study, two interventions, and healthy adults. He added that further validation studies of Brain Flow and Temple’s other proprietary metric, Entropy, were under way.

The startup is also offering to loan its devices to qualified researchers seeking to independently test its metrics, Goyal added.

Temple’s Wearable Bet

Temple is developing a wearable device intended to continuously track signals associated with cerebral blood flow. It describes its device as a product that will measure “brain flow” – the blood flow to the brain. 

Unlike conventional consumer wearables that primarily monitor metrics such as heart rate, blood oxygen levels, and sleep, Temple is betting on measurements taken from the side of the head.

Temple raised around ₹493 Cr earlier this year from investors including Peak XV Partners, Steadview Capital, NK Squared, and Goyal. The round reportedly valued the startup at about ₹1,700 Cr (about $204 Mn).

Its valuation subsequently nearly doubled to $375 Mn as part of an ESOP liquidity programme for early employees.

Last month, Goyal said Temple had reduced the size of the wearable to less than half that of the earlier version. The startup is preparing to open preorders and expects to begin shipping the device before the end of 2026.

Temple also recently acquired London-based longevity medicine practice Longevous for an undisclosed amount, adding clinical and scientific expertise ahead of the wearable’s launch.

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