Methods, devices, and materials that include, in certain embodiments, a mobile device, movable across a surface by a user, that provides ultraviolet light for a process of sanitizing or sterilizing the surface that comprises an ultraviolet light source for illuminating the surface with the ultraviolet light to thereby sanitize or sterilize the surface. The device may include a movement sensor operatively coupled to a microprocessor that receives movement data from the movement sensor, and an indicator that is operatively coupled to the microprocessor, with the microprocessor comprising programming to 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.