PERMID 2005 (just finished in May) is a conference dedicated to exploring the way mobile devices can be used to augment real world interactions. All the papers are available as PDF.
“But why not use these devices for interactions with the real world, as a mediator between the virtual and the userÃ¯Â¿Â½s world? While certain research domains within the fields of mobile applications and services advance at an amazing speed (e.g. context-aware services on mobile devices, using the sensors of mobile phones), the areas of pervasive mobile user interfaces, mobile devices as interaction devices, mobile devices for interactions with the physical world and user experiences in this field are still rather limited.”