It's what we normally would refer to as a "labs" project, a piece of software that resulted from ideas that aren't tied to any actual products. At Microsoft' it's called a "Garage" project that was developed in after-hours work and is now offered as a free download as Mouse Without Borders.
The 1.1MB tool allows users to move their mouse cursor across different screens, even if they are connected to different computers. You can even copy and paste text from and to different screens, send screen captures from one PC to another, or drag files from one PC to another. Up to four different computers can be controlled from a single mouse. Microsoft said that the software was tested internally by 9000 people before it was approved for public release.
We tried it and think it's pretty cool. Why haven't we thought about this before?