Massey Plugins' "Listen" is a funny and unique plug-in that comes as part of the Massey Tools bundle. This is a free bundle of software although isn't featured on Massey's site any more. You should be able to find the Tools bundle in some places, but it was released as the first plug-ins from Steve Massey and aren't supported anymore. The good news is that if you find it, you'll also get a bunch of other free plug-ins, most of which will be more useful than this one. All that Massey Listen does is give you a full screen that says "LISTEN" on it and is designed to help you actually listen to the music rather than following things on the screen. This can actually be more helpful than you think, although the same effect can be had by simply turning off your monitor .
I'm currently running the Massey Plugins Listen plug on my system at home where I use Pro Tools 9 with a Mac Book Pro. It's pointless to really list off all of my specs here as this plug-in will literally work on every system that can run a DAW. You should not be worried at all about performance here as it's really a non issue.
As silly as it might sound, I actually find myself using Massey Plugins Listen quite often. All it does is cover up your DAW with the word "LISTEN," but when doing a listen down it is quite useful to not be distracted by your edit and mix windows, which can sometimes get in the way of your listening. Often I do find myself 'listening visually,' following the faders or waveforms on the screen, which takes you away from what you're actually hearing at time. Of course sometimes this is necessary, but there is a lot to be said for listening with a blank screen. LISTEN isn't really necessary if you turn off your screen sometimes to listen anyway, but being that it's free and you can get it with a bunch of other potentially more useful plug-ins, it's worth checking out.