A bouncer control device for controlling the generally upward and downward motion of a children's bouncer, the bouncer control device comprising: a drive assembly configured to be actuated in order to impart a motive force on the children's bouncer that causes the children's bouncer to bounce, wherein the drive assembly is actuated by electric current; a power supply configured to transmit electric current to the drive assembly; and characterised by: a piezoelectric motion sensor configured to sense the natural frequency of the children's bouncer and generate a frequency signal representative of the natural frequency; and a bouncer control circuit configured to: receive the frequency signal from the piezoelectric motion sensor; and generate a control signal, based at least in part on the received frequency signal, that triggers the power supply to intermittently supply electric current to the drive assembly and thereby cause the drive assembly to impart a motive force on the children's bouncer that causes the bouncer to bounce at a frequency substantially equal to the natural frequency; wherein the piezoelectric motion sensor comprises: a housing (410, 531) defining a longitudinal axis; at least one piezoelectric sensor including a sensing surface positioned within the housing (410, 531); and a weighted member positioned within the housing (410, 531) and configured for movement within the housing (410, 531) in the direction of the housing's longitudinal axis; wherein the weighted member is configured to apply a variable force to the sensing surface of the piezoelectric sensor in response to movement of the children's bouncer, and wherein the frequency signal output by the piezoelectric sensor corresponds to the magnitude of the variable force applied by the weighted member. a drive assembly configured to be actuated in order to impart a motive force on the children's bouncer that causes the children's bouncer to bounce, wherein the drive assembly is actuated by electric current; a power supply configured to transmit electric current to the drive assembly; and characterised by: a piezoelectric motion sensor configured to sense the natural frequency of the children's bouncer and generate a frequency signal representative of the natural frequency; and a bouncer control circuit configured to: receive the frequency signal from the piezoelectric motion sensor; and generate a control signal, based at least in part on the received frequency signal, that triggers the power supply to intermittently supply electric current to the drive assembly and thereby cause the drive assembly to impart a motive force on the children's bouncer that causes the bouncer to bounce at a frequency substantially equal to the natural frequency; a piezoelectric motion sensor configured to sense the natural frequency of the children's bouncer and generate a frequency signal representative of the natural frequency; and a bouncer control circuit configured to: receive the frequency signal from the piezoelectric motion sensor; and generate a control signal, based at least in part on the received frequency signal, that triggers the power supply to intermittently supply electric current to the drive assembly and thereby cause the drive assembly to impart a motive force on the children's bouncer that causes the bouncer to bounce at a frequency substantially equal to the natural frequency; receive the frequency signal from the piezoelectric motion sensor; and generate a control signal, based at least in part on the received frequency signal, that triggers the power supply to intermittently supply electric current to the drive assembly and thereby cause the drive assembly to impart a motive force on the children's bouncer that causes the bouncer to bounce at a frequency substantially equal to the natural frequency; wherein the piezoelectric motion sensor comprises: a housing (410, 531) defining a longitudinal axis; at least one piezoelectric sensor including a sensing surface positioned within the housing (410, 531); and a weighted member positioned within the housing (410, 531) and configured for movement within the housing (410, 531) in the direction of the housing's longitudinal axis; a housing (410, 531) defining a longitudinal axis; at least one piezoelectric sensor including a sensing surface positioned within the housing (410, 531); and a weighted member positioned within the housing (410, 531) and configured for movement within the housing (410, 531) in the direction of the housing's longitudinal axis; wherein the weighted member is configured to apply a variable force to the sensing surface of the piezoelectric sensor in response to movement of the children's bouncer, and wherein the frequency signal output by the piezoelectric sensor corresponds to the magnitude of the variable force applied by the weighted member.