A method executed by a system comprising one or more sensors configured to record sensor data from a monitored scene space, wherein the one or more sensors are or comprise image sensors, wherein the method comprises: recognizing a first two-handed gesture and a second two-handed gesture in the monitored scene space to at least partially define a shape and position of a computer-implemented virtual boundary in a corresponding monitoring space, wherein the first two-handed gesture in the monitored scene space specifies a first two points (p1', p2') in the monitoring space and the second two-handed gesture in the monitored scene space specifies a second two points (p1', p2') in the monitoring space; causing implementation of the computer-implemented virtual boundary in the monitoring space corresponding to the monitored scene space, wherein a shape and position of the computer-implemented virtual boundary is at least defined by the first two points (p1', p2') in the monitoring space and the second two points (p1', p2') in the monitoring space; extending a depth or an area of the computer-implemented virtual boundary outwards from one or more of: the first two points (p1', p2'), and the second two points (p1', p2') towards one or more limits of the monitoring space; wherein the size of the extension is controlled with an extension gesture, and wherein if the extension gesture is a movement that does not stop within a threshold value, then an exterior dimension of the virtual boundary is extended to the limits of the monitoring space, and if the extension gesture is a movement that stops at a point q and does not exceed the threshold value, then the exterior dimension of the virtual boundary is extended to a point corresponding to the point q in the monitoring space; and processing received data from sensors of the monitored scene space to generate a response event in response to a change in at least a portion of the monitored scene space relative to the computer-implemented virtual boundary in the corresponding monitoring space. recognizing a first two-handed gesture and a second two-handed gesture in the monitored scene space to at least partially define a shape and position of a computer-implemented virtual boundary in a corresponding monitoring space, wherein the first two-handed gesture in the monitored scene space specifies a first two points (p1', p2') in the monitoring space and the second two-handed gesture in the monitored scene space specifies a second two points (p1', p2') in the monitoring space; causing implementation of the computer-implemented virtual boundary in the monitoring space corresponding to the monitored scene space, wherein a shape and position of the computer-implemented virtual boundary is at least defined by the first two points (p1', p2') in the monitoring space and the second two points (p1', p2') in the monitoring space; extending a depth or an area of the computer-implemented virtual boundary outwards from one or more of: the first two points (p1', p2'), and the second two points (p1', p2') towards one or more limits of the monitoring space; wherein the size of the extension is controlled with an extension gesture, and wherein if the extension gesture is a movement that does not stop within a threshold value, then an exterior dimension of the virtual boundary is extended to the limits of the monitoring space, and if the extension gesture is a movement that stops at a point q and does not exceed the threshold value, then the exterior dimension of the virtual boundary is extended to a point corresponding to the point q in the monitoring space; and processing received data from sensors of the monitored scene space to generate a response event in response to a change in at least a portion of the monitored scene space relative to the computer-implemented virtual boundary in the corresponding monitoring space. the first two points (p1', p2'), and the second two points (p1', p2') towards one or more limits of the monitoring space; wherein the size of the extension is controlled with an extension gesture, and wherein if the extension gesture is a movement that does not stop within a threshold value, then an exterior dimension of the virtual boundary is extended to the limits of the monitoring space, and if the extension gesture is a movement that stops at a point q and does not exceed the threshold value, then the exterior dimension of the virtual boundary is extended to a point corresponding to the point q in the monitoring space; and processing received data from sensors of the monitored scene space to generate a response event in response to a change in at least a portion of the monitored scene space relative to the computer-implemented virtual boundary in the corresponding monitoring space.