Abstract: Apparatus for supporting a location-based application is disclosed. The apparatus comprises a plurality of mobile devices which report their locations to an application computer. The application computer then periodically or occasionally sends the mobile devices a message (textual, speech, photo or video etc.) which depends upon the reported location of the mobile device. A problem with known apparatus of this type arises when a plurality of users are partaking in the same location-based application together, but receive different messages because their positions are not identical. The location-based application supporting apparatus disclosed here overcomes this problem by first identifying mobile devices which are moving as a group, and then sending all members of that group the same location-based message. The solution is of particular utility in relation to located information, advertising, or reviews for shops, restaurants etc., located games, located educational experiences and location tourism.