US Patent 9418535 Hand-wash monitoring and compliance system

A method and apparatus for monitoring hand-washing compliance can include: detecting sensor readings; calculating movement estimations based on differences between the sensor readings; counting a number of crosses based on how often the movement estimations: are calculated above an upper threshold and are calculated below a lower threshold in consecutive movement calculations, are calculated below the lower threshold and are calculated above the upper threshold in the consecutive movement calculations, or a combination thereof; decrementing a countdown timer based on the number of crosses being above a cross-threshold; and pausing the countdown timer based on the number of crosses being below the cross-threshold.