The invention relates to an electronic add-on module which is fitted releasably onto an automatic injection appliance before the start of injection. The add-on module comprises a force sensor for measuring a time-variable axial force component exerted on or transmitted to the attached add-on module by the injection appliance during an injection procedure. The add-on module also comprises a grip or a preferred grip position for gripping and holding the add-on module and the inserted injection appliance. The add-on module can additionally have a microphone for detection of acoustic signals. A state of the injection appliance can be determined by the add-on module solely on the basis of measurements of the axial force sensor, optionally supplemented by microphone measurements. The invention thus affords a straightforward and cost-effective way of monitoring or controlling the correct performance of an injection procedure carried out with an automatic injection appliance.