Google has introduced a new API called Interactive-Spaces which provides runtime that allows developers to build interactive applications for physical spaces.
Take a look on the screenshot below. You will see that there's a circle under each person. Well, it was taken as soon as a person enters the floor because there were cameras on the ceilings who are doing blob detection.
Interactive Spaces is written in Java, so it can run on any operating
box. Native applications can also be run, which means packages like
openFrameworks which use C++ are also supported out of the box. Plans
are also underway for supporting the Processing language.
This is an initial source release. As the final licenses are finished,
there will be a binary release. Please see Downloads for a PDF file for
documentation. This documentation is in progress.