A method for identifying a subset of one or more mobile computing devices out of a set of mobile computing devices at a venue, each of said mobile computing devices having a display , the method comprising: broadcasting a trigger signal to the set of mobile computing devices at the venue; receiving said trigger signal by the mobile computing devices in the set ; rendering visual content on the displays of the mobile computing devices in the set after reception of the trigger signal; and subsequently causing those mobile computing devices that are not part of said subset to stop rendering said visual content while those mobile computing devices that are part of said subset continue to render said visual content, until only those mobile computing devices that belong to said subset remain rendering said visual content, characterized in that the method further comprises: causing each mobile computing device in the set to create a random time stamp after receiving the trigger signal; causing each mobile computing device to connect to a server and send an identifier request to said server at a point in time that corresponds to the random time stamp; when the server receives an identifier request from a mobile computing device , transmitting an identifier from the server to the corresponding mobile computing device ; determining that the respective mobile computing device is part of the subset if the transmitted identifier meets a match criterion. broadcasting a trigger signal to the set of mobile computing devices at the venue; receiving said trigger signal by the mobile computing devices in the set ; rendering visual content on the displays of the mobile computing devices in the set after reception of the trigger signal; and subsequently causing those mobile computing devices that are not part of said subset to stop rendering said visual content while those mobile computing devices that are part of said subset continue to render said visual content, until only those mobile computing devices that belong to said subset remain rendering said visual content, characterized in that the method further comprises: causing each mobile computing device in the set to create a random time stamp after receiving the trigger signal; causing each mobile computing device to connect to a server and send an identifier request to said server at a point in time that corresponds to the random time stamp; when the server receives an identifier request from a mobile computing device , transmitting an identifier from the server to the corresponding mobile computing device ; determining that the respective mobile computing device is part of the subset if the transmitted identifier meets a match criterion. causing each mobile computing device in the set to create a random time stamp after receiving the trigger signal; causing each mobile computing device to connect to a server and send an identifier request to said server at a point in time that corresponds to the random time stamp; when the server receives an identifier request from a mobile computing device , transmitting an identifier from the server to the corresponding mobile computing device ; determining that the respective mobile computing device is part of the subset if the transmitted identifier meets a match criterion. <EOS>