Deepinder Goyal, the Zomato founder who stepped away from the Eternal CEO role to chase a new mission, has launched Temple – a small, pill-shaped wearable that sticks to the side of your head (between forehead and ear) with adhesive grips.
Priced around ₹85,000 with a lifetime subscription and pre-orders open since early November 2026, it claims to track “Brain Flow” (signals linked to cerebral blood flow and oxygenation), an “Entropy” score for physiological strain, heart rate, and other metrics tied to sleep, stress, exercise, and recovery. Goyal links it to broader ideas around gravity, ageing, and real-time cost of being alive. The company positions it firmly as a fitness/wellness device, not a medical one, and has promised users will later be able to share data with doctors.
The med professionals have raised a lot of questions on the claims and as of now, we don’t see much response from Deepinder on the scientific part.
Key Questions Doctors Are Asking
Here is a point-by-point summary of the main questions and criticisms circulating from doctors on X (primarily @theliverdoc’s threads and replies, plus neurologists such as @hyderabaddoctor and others responding directly to Goyal):
- Brain vs. face/scalp signal
The sensor sits on the superficial temporal artery, which is outside the skull and supplies the face and scalp. How can it isolate true cerebral (brain) blood flow? Doctors argue it primarily measures facial flushing or scalp flow and “has absolutely NOTHING to do with the brain.” Temple’s own science lead has acknowledged in replies that the signal is not yet proven brain-specific in all conditions and that separation from scalp components is incomplete. - Quality and independence of evidence
Why rely on company-funded, small-sample preprints (e.g., groups of ~23 adults or 44 young men) that admit methodological limitations, statistical issues, and lack of outcome studies? Where are the peer-reviewed, independent validations with proper reference standards (such as transcranial Doppler or NIRS under real-world conditions)? - Comparison to established wearables
Goyal cited Whoop and others that launched on internal work first. Doctors counter that Apple Watch, Fitbit, Samsung, Oura and Whoop had stronger pre-launch clinical data, multi-site trials, peer-reviewed studies, and (for specific features) FDA clearances. Why open ₹85,000 pre-orders with zero regulatory approvals and only internal preprints? - Tangible consumer benefit and head-to-head data
If it is “just a fitness tracker,” what does it offer that existing validated devices do not? Why no head-to-head studies proving non-inferiority or superiority at this price point? - Actionability and clinical relevance
What decision should a healthy, asymptomatic user make from a “Brain Flow” or Entropy reading? Neurologists note that continuous cerebral perfusion monitoring has limited proven value outside specific clinical or research settings and can create unnecessary anxiety. - Refund / return policy specifics
Goyal has repeatedly highlighted the 14-day, no-questions-asked return policy (which he notes even Apple does not offer in India) as proof the product must deliver or the company fails quickly. Doctors and critics push back: a 14-day window tests comfort, adhesion, and basic usability, but how does a user at home detect whether the physiological readings themselves are accurate or systematically wrong? A smooth, repeatable but incorrect graph can still pass a short return window. Some also flagged the framing of the policy discussion as condescending toward Indian buyers. - Framing shift and marketing claims
Why market strong brain-flow and longevity claims (including gravity-ageing ideas) and then emphasise “we are not a medical device / fitness tracker only” once scrutiny intensifies? Critics say the device has not been proven even as a superior fitness tracker. - Additional practical questions raised
- What is the individual-level error, bias, and limits of agreement for Brain Flow readings versus reference methods?
- How much does motion, sensor placement, temperature, or scalp blood flow affect the signal in daily use?
- Why take pre-order money while key limitations remain acknowledged by the science team and independent studies are still “planned”?
Goyal and the Temple team maintain that the science is sound enough to ship, more validation (including preprints and independent work) is coming, incentives are aligned with long-term success, and the return policy plus heavy personal investment make a scam irrational. They stress the device is wellness-oriented and that some of the most interesting features have not yet been revealed.
Where Things Stand
The debate is classic early-stage hardware vs. scientific scrutiny. Temple has opened pre-orders and is shipping in limited numbers. Doctors continue to demand stronger, independent data before consumers spend ₹85,000. Goyal continues to defend the vision and the process (and the fact that he himself has put $30mn in this venture).
Whether the 14-day return window and real-world user data will quiet the critics, or whether the questions about signal specificity and validation will intensify, will become clearer once devices reach customers in 2027