Yeah. The developers at barbarian mentioned in a blog post that they started the project since they needed a browser with fullscreen support for mac to present slides. But I personally use this to browse things where I need concentration - like reading some serious stuff.

And there is a "Kiosk mode" which would prevent me from doing an alt+tab. To come out of kiosk mode I would have to type my password once. When the password prompt comes up I would ask myself once if I need to really go to some other app now, or if I should continue concentrating on reading this for more time. This process makes me concentrate longer on what I'm reading.