1. A computer-implemented method of triggering an instance of companion software to perform an expected action related to a piece of media content during a delivery of that media content by a media device to a content consuming user, the method comprising: the instance of the companion software receiving a synchronization signal transmitted when, in delivering the media content, the media device reaches a reference point in the media content, wherein the synchronisation signal conveys a time instant of that reference point; measuring a current elapsed time from the time instant of the reference point; determining a local confidence value based on the current elapsed time and/or based on a determined reliability of a carrier signal used to convey the received synchronization signal, the local confidence value indicative of the likelihood of the expected action being triggered at a correct time, the correct time being when the media device, in delivering the media content, reaches the trigger point; accessing computer storage holding an association of the expected action with a time instant of a trigger point in the media content; and triggering the expected action when the current elapsed time substantially matches the time instant of the trigger point conditional on the local confidence value being within a first confidence value limit.