Embodiments according to at least some aspects of the present disclosure comprise methods, apparatus, devices, and/or systems pertaining to bathtub monitors that may be configured to sense motion and/or absence of motion, such as motion associated with an occupant of a bathtub. Some example embodiments may be configured to provide local and/or remote alarm(s) upon detection of a potentially unsafe condition, such as an absence of motion of the occupant of a bathtub. In some example embodiments, a bathtub alarm system may comprise an accelerometer to sense movement (or lack of movement) in the tub by sensing changes in gravitational forces within the tub.