This paper introduces an ultrathin, compliant skin-like sensor/actuator technology designed to provide precise and continuous thermal characterization of human skin. The devices, which can be laminated onto the epidermis, offer non-invasive spatial mapping of skin temperature with millikelvin precision and simultaneous assessment of tissue thermal conductivity. Key features include microscale temperature sensors that act as micro-heaters, integrated with thin, low modulus elastic sheets. The sensors rely on thin metal serpentine features or PIN diodes constructed with silicon nanomembranes, ensuring mechanical properties and geometries matched to human tissue. The devices provide soft, conformal contact with the epidermis, minimizing irritation and measurement artifacts. Experimental results demonstrate the devices' ability to measure subtle variations in skin temperature associated with mental activity, physical stimulation, and vasoconstriction/dilation, as well as to accurately determine skin hydration through thermal conductivity measurements. The technology has potential applications in clinical settings for real-time health monitoring and diagnostic tools.This paper introduces an ultrathin, compliant skin-like sensor/actuator technology designed to provide precise and continuous thermal characterization of human skin. The devices, which can be laminated onto the epidermis, offer non-invasive spatial mapping of skin temperature with millikelvin precision and simultaneous assessment of tissue thermal conductivity. Key features include microscale temperature sensors that act as micro-heaters, integrated with thin, low modulus elastic sheets. The sensors rely on thin metal serpentine features or PIN diodes constructed with silicon nanomembranes, ensuring mechanical properties and geometries matched to human tissue. The devices provide soft, conformal contact with the epidermis, minimizing irritation and measurement artifacts. Experimental results demonstrate the devices' ability to measure subtle variations in skin temperature associated with mental activity, physical stimulation, and vasoconstriction/dilation, as well as to accurately determine skin hydration through thermal conductivity measurements. The technology has potential applications in clinical settings for real-time health monitoring and diagnostic tools.