Method and apparatus to sense hydration level of a person

A hydration sensor for measuring the hydration level of a user based on the user's saliva, comprising:

• a digital timing device providing a timing indication;
• and
• a disposable sensing element including:
• a piece of water-permeable material having a first side and a second side, with a chemical compound coupled to the first side;
• a first piece of water-impermeable material coupled to the first side of the water-permeable material, over the chemical compound;
• and
• a second piece of water-impermeable material coupled to the second side of the piece of water-permeable material,
• wherein the disposable sensing element does not include an electronic device,
• wherein the disposable sensing element includes at least one aperture that allows saliva in the mouth of the user to reach the water-permeable material, and to the chemical compound via the water-permeable material,
• wherein the chemical compound is configured to change color of at least a portion of the water-permeable material due to contact with saliva and the change is observable from at least a portion of one piece of the water-impermeable material,
• wherein at least a portion of the disposable sensing element is configured to be placed in the mouth of the user to measure the hydration level of the user, and the disposable sensing element may be disposed after the element has been placed in the mount of a user to measure hydration level, and
• wherein the hydration sensor further includes an indicator, the indicator to provide an indication for the hydration level of the user, based on time measurement regarding color change of the at least a portion of the water-permeable material, after the disposable sensing element is placed in the mouth of the user, via the timing indication.