A mobile device, movable across a surface by a user, that provides ultraviolet light for a process of sanitizing or sterilizing the surface that comprisesan ultraviolet light source for illuminating the surface with the ultraviolet light to thereby sanitize or sterilize the surface,a movement sensor operatively coupled to a microprocessor that receives movement data from the movement sensor, andan indicator that is operatively coupled to the microprocessor,with the microprocessor comprising programmingto perform calculations comprising the movement data and an intensity of the light at the surface to calculate a calculated dosage of the light at the surface andto perform a comparison of the calculated dosage to a predetermined dosage,wherein the microprocessor, based on the comparison, controls the indicator to provide instructions to the user.A method of making a mobile device movable across a surface by a user for sanitizing or sterilizing the surface comprisingmounting an ultraviolet light source on the mobile device in a position on the device for illuminating the surface with the ultraviolet light to thereby sanitize or sterilize the surface,mounting a movement sensor on the device, wherein the sensor is operatively coupled to a microprocessor that receives movement data from the movement sensor when the device is moved, andproviding an indicator that is operatively coupled to the microprocessor,with the microprocessor comprising programmingto perform calculations comprising the movement data and an intensity of the light at the surface to calculate a calculated dosage of the light at the surface andto perform a comparison of the calculated dosage to a predetermined dosage,wherein the microprocessor, based on the comparison, controls the indicator to provide instructions to the user.A method of sanitizing or sterilizing a surface with ultraviolet light using a mobile device comprising,moving the device across a surface and illuminating the surface with the ultraviolet light to provide a dosage of light that sterilized or sanitizes the surface,adjusting a rate of movement of the device in response to instructions provided by an indicator indicating a level of completion of the sanitizing or sterilizing process for the surface,with the level of completion based on a comparison of a light dosage applied to the surface as compared to a predetermined dosage of the light.