A supplemental device for gathering information concerning the use of an injection device, the supplemental device having 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, and at least one processor. The 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, and if it is determined the rotational speed of the object does exceed the threshold speed, to refrain from attempting to identify the feature.