16. A computing device comprising: one or more processors arranged to render a document at a display device using output of an application which is executing on the computing device or at a remote computing entity in communication with the computing device, the application configured to at least one of read or write documents; one or more sensors monitoring user annotation events associated with the rendered document; the one or more processors arranged to monitor state data of the application during monitoring of the annotation events by the sensors; a gesture recognition component arranged to recognize gestures by analyzing the received sensor data; and a memory storing the state data with associated timestamps, the memory storing the recognized gestures with associated timestamps; the one or more processors arranged to calculate a compressed record of the sensor data on the basis of the recognized gestures, the state data, and the timestamps; the one or more processors arranged to display representations of the recognized gestures superimposed on representations of portions of the rendered document associated with the recognized gestures, wherein individual ones of the representations of the recognized gestures are distinguishable from each other.
16. A computing device comprising: one or more processors arranged to render a document at a display device using output of an application which is executing on the computing device or at a remote computing entity in communication with the computing device, the application configured to at least one of read or write documents; one or more sensors monitoring user annotation events associated with the rendered document; the one or more processors arranged to monitor state data of the application during monitoring of the annotation events by the sensors; a gesture recognition component arranged to recognize gestures by analyzing the received sensor data; and a memory storing the state data with associated timestamps, the memory storing the recognized gestures with associated timestamps; the one or more processors arranged to calculate a compressed record of the sensor data on the basis of the recognized gestures, the state data, and the timestamps; the one or more processors arranged to display representations of the recognized gestures superimposed on representations of portions of the rendered document associated with the recognized gestures, wherein individual ones of the representations of the recognized gestures are distinguishable from each other. 18. A computing device according to claim 16 the gesture recognition component being at least partially implemented using hardware logic selected from any one or more of: a field-programmable gate array, a program-specific integrated circuit, a program-specific standard product, a system-on-a-chip, a complex programmable logic device, or a graphics processing unit.