15. An apparatus comprising: one or more processors and a memory; input means for receiving, from a user interface, an annotation associated with a background image; control means for adding the annotation to a queue of pending annotations; output means for transmitting the annotation from the apparatus to a server; wherein the control means removes the annotation from the queue of pending annotations, and adds the annotation to a list of acknowledged annotations, when an acknowledgment of the annotation is received by the apparatus from the server; wherein the output means generates a display image comprising the background image, annotations in the list of acknowledged annotations, and annotations in the queue of pending annotations; and wherein the one or more processors and the memory cooperate to implement at least in part the input, output and control means.
15. An apparatus comprising: one or more processors and a memory; input means for receiving, from a user interface, an annotation associated with a background image; control means for adding the annotation to a queue of pending annotations; output means for transmitting the annotation from the apparatus to a server; wherein the control means removes the annotation from the queue of pending annotations, and adds the annotation to a list of acknowledged annotations, when an acknowledgment of the annotation is received by the apparatus from the server; wherein the output means generates a display image comprising the background image, annotations in the list of acknowledged annotations, and annotations in the queue of pending annotations; and wherein the one or more processors and the memory cooperate to implement at least in part the input, output and control means. 19. The apparatus of claim 15 : wherein the control means removes one or more coordinates from the annotation before transmitting the annotation.