Theory
The commodity component assumption
Do not design bespoke electronics unless a commodity part is demonstrably inadequate for the claim being made. The burden of proof sits with the custom design, the same way Zero Neo puts it on new software.
The assumption, stated so it can be falsified
Claim: hypothesis
For a given medical claim, the sensing, compute, radio, storage, and power required can be met by components already manufactured at consumer scale, and any custom electronics must justify itself against a named inadequacy in a specific commodity part.
That is falsifiable, and it should be falsified often. The useful output is not a list of devices we could build. It is a growing list of named inadequacies: this part drifts with temperature, that radio cannot meet the latency requirement, this optical path cannot be calibrated in a wearable form factor. Each one is a real engineering fact that a market report will not give you.
Why the assumption is plausible
Claim: inference
Volume buys reliability data no medical production run can match. A sensor shipped in hundreds of millions of phones has field statistics that a device shipping ten thousand units a year will never accumulate. That does not make it fit for a medical claim, but it does make the reliability argument arguable, which is more than a bespoke part can offer on day one.
Volume also buys supply, second sources, tooling, reference designs, and firmware that already works. The cost of the part is often the smallest part of what commoditization provides.
Why it fails
Claim: inference
Consumer parts are specified for consumer use. Drift, tolerance, temperature range, and lifetime are specified for a phone replaced every three years, not for a device that must hold accuracy for seven. End-of-life notices arrive on the vendor's schedule, and a component change in a cleared device is a change-control obligation, not an inconvenience.
So the assumption is a starting posture, not a conclusion. It says start here and prove you must leave, rather than start custom and never ask.