T. Sohn, K. A. Li, G. Lee, I. Smith, J. Scott, and W. G. Griswold. Place-its: A study of location-based reminders on mobile phones. In UbiComp’05: Seventh International Conference on Ubiquitous Computing, pages 232–250, Tokyo, Japan, September 2005. [pdf]

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This paper presents the Place-Its system, a context-aware reminder platform that is used by the user to define reminders that are triggered by specific locations. This application is said to improve the usefulness of automated reminders.

The aim of this study was to find how location-based reminders are used when available through a person’s day. The study builds on previous work on ActiveCampus, ComMotion \cite{Marmasse:2000fs}, and CybreMinder, highlighting the fact that these previous studies used additional hardware, such as GPS receivers, that people do not carry around or because they are restricted to predefined areas.

The three components of a Place-It note are the trigger, the text and the place. The trigger defines whether the message should be signaled upon arrival or departure of the associated place. The text is the message associated with the reminder and the place is the location defined by the user where the reminder should activate. Location sensing is achieved with PlaceLab \cite{Smith:2005tr}.

The authors conducted a user study with 10 subjects during a period of two weeks. They interviewed the subjects before and after the experiments, collecting interesting facts. One interesting finding was the unexpected presence of ‘motivators’ reminders, a kind of message used to motiva the person to perform a cerain task.

Due to the way location-based reminders were used and the relative inaccuracy of location-sensing in Place-Its, the author could not claim location to be essential context to prompt reminders. The location-sensing ready availability in Place-Its admits opportunistic use by those who can map relevant (but unsensed) context to anticipated, coarse, location cues. Participants who worked by a set time schedule achieved similar results by mapping their relevant context to time cues and modifying their behavior.

Results showed that location was widely used ad a cue for other contextual information. It appeared that the convenience and ubiquity of location-sensing provided outweights some of the current weakness of the system.

Tags: interaction design, Location Based Services, tagging, ubiquitous computing