a system and method are described for location - based and group - based operations on a data processing device . for example , a computer - implemented method according to one embodiment of the invention comprises : establishing a buddy group containing identities of a plurality of users within the group and notification data indicating when other users are to be notified about current locations of the users in the group ; determining whether wireless data processing devices of two or more users of the buddy group are at the same location or within a particular distance of the location ; identifying the users and the location ; and notifying other users in the group of the identity of the users and the location .