TunnelVision is described as 'allows you to hide the parts of the screen where your mouse cursor is not, effectively increasing privacy (though at a cost)' and is an app in the Security & Privacy category. There are three alternatives to TunnelVision for Windows. The best alternative is Cinemadrape, which is free. Other great apps like TunnelVision are LeDimmer (Free) and Zorro (Free).
CinemaDrape helps you focus on your current task on the screen (such as a video in a web page, a photo or a document editor area) by instantly blanking or dimming the other less important areas in a web page or in the background windows.
Zorro is a utility to completely blank the screen except for a rectangular area selected by the user. This is especially useful for watching videos on your computer without being distracted by other programs.