Almost every feed you use is optimized for behavioural signals: how long you watched, whether you finished, whether you came back. These are not cynical choices. They are the only signals that have ever been cheaply available at scale. But they are proxies. Attention is not satisfaction, and time spent is not time well spent. A system optimizing hard against a proxy will eventually find where the proxy and the real goal come apart, and settle there. That is not a hypothetical failure mode; it is the ordinary experience of most people's evenings.

Roughly 80 million U.S. adults now wear a device that measures cardiac activity, variability, movement and sleep continuously. For the first time there is an objective, longitudinal signal about how someone is actually doing, one that does not depend on asking them. Nutrition had the same gap until continuous glucose monitors made the effect of a particular meal visible per person, and a category grew around what people could suddenly see. Content has no equivalent, though what you watch also moves heart rate, arousal and sleep.

Wristream is a recommendation system whose objective includes how you physiologically responded to what it showed you. It learns per person rather than per population, since the same clip does different things to different people, and it treats well-being as a hard constraint rather than a preference: some content simply does not get to be eligible, however engaging it would be. The longer aim is infrastructure, since the same loop could order anything where sequence and state matter. 529 Tech has a patent pending with the USPTO covering the core system, and the central claim is being tested with real participants under independent IRB review.