Mediating Multi-Party Negotiation Through Marker-Based Tracking of Mobile Phones Michael Rohs, Deutsche Telekom Laboratories, TU Berlin, Germany Christian Kray, Informatics Research Institute, Newcastle University, UK Abstract Negotiating a date and a time for a meeting involving a number of people can be a difficult and time-consuming process - even when all participants are collocated and supported by technology. Oftentimes, it involves an auction- like procedure, where suggestions and conflicts are announced to the group and then checked individually until a feasible time can be found. We propose to use spatial proximity regions around handheld devices to significantly reduce the effort of exploring proposed meeting times in the context of a party of collocated people. In order to determine the location of devices on a table, we have developed a new tracking mechanism that relies on dynamic visual markers shown on the screen of the devices used. A preliminary evaluation of the underlying idea and the tracking mechanisms highlights advantages and drawbacks of our approach.