Medical injections and related devices and methods

An autoinjector comprising:

• a housing comprising a recessed portion;
• a needle arranged at a distal end of the housing;
• a needle guard configured to expose the needle when an insertion force is applied to insert the needle into a user;
• a container disposed within the housing and configured to contain medicament;
• a plunger slidably disposed within the container;
• a plunger rod configured to push the plunger through the container to dispense the medicament through the needle when the container contains medicament and when the needle is exposed, wherein the plunger rod comprises a magnetic region, and wherein a dispensing movement of the plunger rod generates a first magnetic signal;
• and
• an attachable module configured to be reversibly attached to the recessed portion of the housing, wherein the attachable module comprises a first sensor configured to detect said first magnetic signal as the plunger rod moves.