A timing device comprises a sensing material and/or a component which is sensitive to the presence of an environmental attribute. The environmental attribute drives and speeds up or slows the timing device as the concentration of the attribute increases or decreases, respectively. Alternatively, the timing device is activated upon sensing the presence of the environmental attribute and indicates a total passage of time from exposure/activation of the timing device. Particularly, sensing materials of varying types are able to be used to indicate exposure to a variety of substances. For example, in some embodiments, the timing device comprises a sensing material which is sensitive to the presence of ultraviolet radiation. Alternatively, the sensing material is sensitive to other variables such as x-ray radiation and nuclear radiation. In further embodiments, the sensing material is sensitive to biological or physical contamination.

A timing device for indicating the passage of a duration of time is disclosed. The timing device and system, in accordance with the embodiments of the invention, comprise an electrochemical component which generates a visual and/or audio indication of the passage of time. The timing device further comprises a compensating element, such as a varistor, a thermistor and/or combinations thereof. The compensating element regulates the response of the device with respect to changes in temperature. The timing device is configured to indicate the passage of a single duration of time or comprises zones that are activated in a range of prescribed times and individually or collectively indicate the passage of time or the passage of a range of times.

A timing device for indicating the passage of a duration of time is disclosed. The timing device and system, in accordance with the embodiments of the invention, comprise an electrochemical component which generates a visual and/or audio indication of the passage of time. The timing device further comprises a compensating element, such as a varistor, a thermistor and/or combinations thereof. The compensating element regulates the response of the device with respect to changes in temperature. The timing device is configured to indicate the passage of a single duration of time or comprises zones that are activated in a range of prescribed times and individually or collectively indicate the passage of time or the passage of a range of times.

A method and system for calibrating a wireless sensor device are disclosed. In a first aspect, the method comprises determining a vertical calibration vector and determining a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes. In a second aspect, a wireless sensor device comprises a processor and a memory device coupled to the processor, wherein the memory device includes an application that, when executed by the processor, causes the processor to determine a vertical calibration vector and to determine a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes.

A method and system for calibrating a wireless sensor device are disclosed. In a first aspect, the method comprises determining a vertical calibration vector and determining a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes. In a second aspect, a wireless sensor device comprises a processor and a memory device coupled to the processor, wherein the memory device includes an application that, when executed by the processor, causes the processor to determine a vertical calibration vector and to determine a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes.

A timing device comprises a sensing material and/or a component which is sensitive to the presence of an environmental attribute. The environmental attribute drives and speeds up or slows the timing device as the concentration of the attribute increases or decreases, respectively. Alternatively, the timing device is activated upon sensing the presence of the environmental attribute and indicates a total passage of time from exposure/activation of the timing device. Particularly, sensing materials of varying types are able to be used to indicate exposure to a variety of substances. For example, in some embodiments, the timing device comprises a sensing material which is sensitive to the presence of ultraviolet radiation. Alternatively, the sensing material is sensitive to other variables such as x-ray radiation and nuclear radiation. In further embodiments, the sensing material is sensitive to biological or physical contamination.

A timing device comprises a sensing material and/or a component which is sensitive to the presence of an environmental attribute. The environmental attribute drives and speeds up or slows the timing device as the concentration of the attribute increases or decreases, respectively. Alternatively, the timing device is activated upon sensing the presence of the environmental attribute and indicates a total passage of time from exposure/activation of the timing device. Particularly, sensing materials of varying types are able to be used to indicate exposure to a variety of substances. For example, in some embodiments, the timing device comprises a sensing material which is sensitive to the presence of ultraviolet radiation. Alternatively, the sensing material is sensitive to other variables such as x-ray radiation and nuclear radiation. In further embodiments, the sensing material is sensitive to biological or physical contamination.

A method and wireless sensor device for determining a time period a person is in bed. In one aspect, a method includes utilizing a wireless sensor device to obtain a plurality of acceleration samples in relation to at least one axis associated with a person's body over a predetermined time window. The method also includes calculating a polar angle for each acceleration sample within the predetermined time window. The method also includes calculating a fraction of an amount of time within the predetermined time window that the polar angle is greater than an angle threshold that indicates that the person is lying down, where if the fraction is greater than a predetermined threshold, the predetermined time window is marked as a period the person is lying down.