Electrochemical indicators are configured to indicate a variable such as time and/or a temperature excursion. In some embodiments, the electrochemical indicators comprise an anode layer and a cathode layer which contact an electrolyte to activate each indicator. In some embodiments, the electrochemical indicator comprises an electrically isolated RFID chip and an RFID antenna which are placed in electrical communication in response to the external variable. The completed RFID tag may then be read by an RFID reader. A completed RFID tag may also be incorporated within the electrochemical indicators comprising an anode layer and a cathode layer and where the RFID tag is unshielded and becomes readable as the indicator expires.

Electrochemical indicators are configured to indicate a variable such as time and/or a temperature excursion. In some embodiments, the electrochemical indicators comprise an anode layer and a cathode layer which contact an electrolyte to activate each indicator. In some embodiments, the electrochemical indicator comprises an electrically isolated RFID chip and an RFID antenna which are placed in electrical communication in response to the external variable. The completed RFID tag may then be read by an RFID reader. A completed RFID tag may also be incorporated within the electrochemical indicators comprising an anode layer and a cathode layer and where the RFID tag is unshielded and becomes readable as the indicator expires.

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.

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.

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 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.

Systems and methods are presented for a timing device. The timing device includes a first electrode, a second electrode, and an electrolyte. The electrolyte includes a material selected such that an electrodeposit forms on the first electrode when a current is applied between the first electrode and the second electrode. A measurable electrical characteristic of the timing device is indicative of a time-dependent degree of growth of the electrodeposit between the first electrode and the second electrode.

Systems and methods are presented for a timing device. The timing device includes a first electrode, a second electrode, and an electrolyte. The electrolyte includes a material selected such that an electrodeposit forms on the first electrode when a current is applied between the first electrode and the second electrode. A measurable electrical characteristic of the timing device is indicative of a time-dependent degree of growth of the electrodeposit between the first electrode and the second electrode.