I read the paper on how it is possible to have a portable device that can identify its exact location in a room within a few centimeters. The device built for this uses a webcam and projector to identify location. The projector can display a grid on the wall in front of the camera, and using the geometry of the grid, identify the location and orientation of the camera relative to that wall.
I found this paper interesting because it is possible that components of a smart home may have some behavior based on where they are in the home. Devices such as the Roomba could already have a use for a device that can give the roomba an exact location in the room. Also, this particular technology does not require an infrastructure in the room, so houses would not have to be built with the devices in mind.
The biggest downside with the current device mentioned in this paper is that the prototype was fairly large and cumbersome. This would make adding to other devices and robots difficult. However, the paper did propose many methods of shrinking the device to something more usable. One such possibility would be to use some sort of laser projector that can be much smaller and use much less power than a traditional projector.