A method for a processor to control a user-interface of a wearable computer or a device connected to the wearable computer, the method for the processor comprising: receiving, from one or more sensors, sets of values describing three-dimensional motion at periodic time points that are taken together to form a measurement time interval; calculating, by the processor, based on the corresponding set of values, a meta acceleration value for each of the periodic time points received during the measurement time interval; determining, by the processor, two distinct quiescent time intervals based on the calculated meta acceleration values; determining, by the processor, a gesture time interval between the two distinct quiescent time intervals; calculating, by the processor, sets of statistical values corresponding to each of the sets of values within the gesture time interval; classifying, by the processor, the sets of statistical values, thereby identifying a corresponding impact gesture of a wrist or fingers of a user wearing the wearable computer; and initiating, by the processor, a predefined response on the user interface of the wearable computer or the device connected to the wearable computer; wherein the predefined response corresponds to the identified impact gesture; wherein the gesture time interval is a period between the two distinct quiescent time intervals in the measurement time interval; wherein the two distinct quiescent time intervals have a set of contiguous time points with absolute maximum values less than a predefined threshold value; and wherein the sets of statistical values are calculated for time points between the two distinct quiescent time intervals. receiving, from one or more sensors, sets of values describing three-dimensional motion at periodic time points that are taken together to form a measurement time interval; calculating, by the processor, based on the corresponding set of values, a meta acceleration value for each of the periodic time points received during the measurement time interval; determining, by the processor, two distinct quiescent time intervals based on the calculated meta acceleration values; determining, by the processor, a gesture time interval between the two distinct quiescent time intervals; calculating, by the processor, sets of statistical values corresponding to each of the sets of values within the gesture time interval; classifying, by the processor, the sets of statistical values, thereby identifying a corresponding impact gesture of a wrist or fingers of a user wearing the wearable computer; and initiating, by the processor, a predefined response on the user interface of the wearable computer or the device connected to the wearable computer; wherein the predefined response corresponds to the identified impact gesture; wherein the gesture time interval is a period between the two distinct quiescent time intervals in the measurement time interval; wherein the two distinct quiescent time intervals have a set of contiguous time points with absolute maximum values less than a predefined threshold value; and wherein the sets of statistical values are calculated for time points between the two distinct quiescent time intervals.