I first saw it as a portable second screen for a computer, and it is that. The advantage is that the Monitor2Go can fold up in its metallic shell and travel with you quite easily. If you have an outlet handy, you just plug it in, then plug it in to your laptop, and you have an easy second screen.
As someone who is currently working on a book, I can honestly say that I absolutely love having a second screen. This way, I can check my Sources and write on my primary screen.
In addition to getting something extra out of your laptop, this is also great for iPad owners. There is a slot for versions of the iPad 2-4, as well as the mini. It is perfect for presentations, and you can turn the screen many directions.
Another great feature is that you can connect an HDMI cable from your smartphone into this Monitor2Go, and you will have both video and audio (provided you have headphones).
You can purchase this Monitor2Go on the MMT site for about $299.