A stylus for use with a computing device, comprising: a housing, wherein the housing has an outer surface; a tip-switch operatively coupled to the housing, wherein the tip-switch is responsive to an applied force; control circuitry to detect the magnitude of the force applied to the tip-switch and to produce a signal representing said magnitude, wherein the control circuitry is operable to detect whether a threshold level of the magnitude of the force applied to the tip-switch is exceeded; an antenna to transmit the signal representing the magnitude of the force applied to the tip-switch to the computing device; wherein if the force applied to the tip-switch is less than or equal to the threshold value, the signal is set to zero, encoded and transmitted and if the force applied to the tip-switch is greater than the threshold value then the detected magnitude of the applied force is encoded and transmitted; and a manual switch; characterised in that: at least a portion of the outer surface of the housing is retro-reflective; and the control circuitry is configured to override the tip-switch using the manual switch by, in response to activation of the manual switch, setting the signal representing the magnitude of the force applied to the tip-switch to an override value and encoding and transmitting the signal to the computing device, wherein the stylus becomes operable to annotate or draw in three-dimensional space, without the tip-switch making contact with an object, when no force is applied to the tip-switch. a housing, wherein the housing has an outer surface; a tip-switch operatively coupled to the housing, wherein the tip-switch is responsive to an applied force; control circuitry to detect the magnitude of the force applied to the tip-switch and to produce a signal representing said magnitude, wherein the control circuitry is operable to detect whether a threshold level of the magnitude of the force applied to the tip-switch is exceeded; an antenna to transmit the signal representing the magnitude of the force applied to the tip-switch to the computing device; wherein if the force applied to the tip-switch is less than or equal to the threshold value, the signal is set to zero, encoded and transmitted and if the force applied to the tip-switch is greater than the threshold value then the detected magnitude of the applied force is encoded and transmitted; and a manual switch; characterised in that: at least a portion of the outer surface of the housing is retro-reflective; and the control circuitry is configured to override the tip-switch using the manual switch by, in response to activation of the manual switch, setting the signal representing the magnitude of the force applied to the tip-switch to an override value and encoding and transmitting the signal to the computing device, wherein the stylus becomes operable to annotate or draw in three-dimensional space, without the tip-switch making contact with an object, when no force is applied to the tip-switch. at least a portion of the outer surface of the housing is retro-reflective; and the control circuitry is configured to override the tip-switch using the manual switch by, in response to activation of the manual switch, setting the signal representing the magnitude of the force applied to the tip-switch to an override value and encoding and transmitting the signal to the computing device, wherein the stylus becomes operable to annotate or draw in three-dimensional space, without the tip-switch making contact with an object, when no force is applied to the tip-switch.