Nature Biomedical Engineering, Published online: 23 June 2026; doi:10.1038/s41551-026-01727-2 Consumer wearables can measure physiological parameters indicative of health, blurring the boundary between wellness products and medical tools. We critically evaluate the FDA’s 2026 guidance on consumer wearables and sensor-based technologies with regard to validation standards, safety risks, definitional coherence and effects on healthcare integration.