An appendage mountable electronic system, said system comprising: a flexible or stretchable substrate having an inner surface and an outer surface, wherein the inner surface defines an enclosure capable of receiving an appendage having a curved surface; and a flexible or stretchable electronic device comprising one or more sensors, actuators or both supported by the inner surface and the outer surface of said flexible or stretchable substrate; said sensors, actuators or both comprising one or more inorganic semiconductor components, one or more metallic components, or one or more inorganic semiconductor components and one or more metallic components (53, 54); wherein at least a portion of said inorganic semiconductor components, metallic components or both has a thickness less than or equal to 500 microns; wherein said flexible or stretchable substrate and said flexible or stretchable electronic device provide a net bending stiffness of the appendage mountable electronic system low enough such that the inner surface of the flexible or stretchable substrate and one or more sensors, actuators or both supported by the inner surface of the flexible or stretchable substrate are capable of establishing conformal contact with a surface of said appendage provided within said enclosure; wherein the flexible or stretchable electronic device is supported by the inner surface and by the outer surface to form a pressure or force sensor having aligned and paired electronic devices on both the inner and outer surface that communicate with each other to provide an output that varies with separation distance between the electronic surfaces, wherein the output depends on a thickness of the flexible or stretchable substrate between the aligned and paired electronic devices, wherein the thickness of the flexible or stretchable substrate in turns depends on the applied pressure or force, the system being characterized in that the paired electronic devices comprise: a heat source and sensor that provide a measure of temperature; or an optical source and optical detector that provide a measure of a light property, such as optical intensity. a flexible or stretchable substrate having an inner surface and an outer surface, wherein the inner surface defines an enclosure capable of receiving an appendage having a curved surface; and a flexible or stretchable electronic device comprising one or more sensors, actuators or both supported by the inner surface and the outer surface of said flexible or stretchable substrate; said sensors, actuators or both comprising one or more inorganic semiconductor components, one or more metallic components, or one or more inorganic semiconductor components and one or more metallic components (53, 54); wherein at least a portion of said inorganic semiconductor components, metallic components or both has a thickness less than or equal to 500 microns; wherein said flexible or stretchable substrate and said flexible or stretchable electronic device provide a net bending stiffness of the appendage mountable electronic system low enough such that the inner surface of the flexible or stretchable substrate and one or more sensors, actuators or both supported by the inner surface of the flexible or stretchable substrate are capable of establishing conformal contact with a surface of said appendage provided within said enclosure; wherein the flexible or stretchable electronic device is supported by the inner surface and by the outer surface to form a pressure or force sensor having aligned and paired electronic devices on both the inner and outer surface that communicate with each other to provide an output that varies with separation distance between the electronic surfaces, wherein the output depends on a thickness of the flexible or stretchable substrate between the aligned and paired electronic devices, wherein the thickness of the flexible or stretchable substrate in turns depends on the applied pressure or force, the system being characterized in that the paired electronic devices comprise: a heat source and sensor that provide a measure of temperature; or an optical source and optical detector that provide a measure of a light property, such as optical intensity. a heat source and sensor that provide a measure of temperature; or an optical source and optical detector that provide a measure of a light property, such as optical intensity.