A supplemental device for gathering information concerning the use of an injection device, the supplemental device comprising:a first camera sensor portion for generating a first camera output indicative of a scene in the field of view of the first camera sensor portion；a second camera sensor portion for generating a second camera output indicative of a scene in the field of view of the second camera sensor portion； andat least one processor configured:to use the first camera output to determine whether a rotational speed of an object in the field of view exceeds a threshold speed；if it is determined the rotational speed of the object does not exceed the threshold speed, to process the second camera output to identify a feature provided on the or another object； andif it is determined the rotational speed of the object does exceed the threshold speed, to refrain from attempting to identify the feature.
