Abstract: Means, apparatus, and methods of sensor/sensory, meta-sensory, and meta-sensing user-interfaces are provided. In one embodiment, smart headwear senses at least one health or mental health parameter of a wearer of the smart headwear. In one embodiment a smart eyeglass senses brain activity. In another embodiment a wearable device senses blood flow, and indirectly through artificial intelligence, other health parameters such as fever, brain health, mental health, and the like. In another embodiment, a wearable AI (Artificial Intelligence) device has associated with it a meta-lock-in amplifier, i.e. a second lock-in amplifier responsive to an output of a first lock-in amplifier, where the first lock-in amplifier is referenced to at least one alternating current electrical signal driving a light source, and the second lock-in amplifier is referenced to an output of the first lock-in amplifier.