I am normally not a "nay sayer", but I can see so many things wrong with that.
You have a fair amount of weight far behind the rear wheels (even if only a couple hundred pounds), then add the substantial drag and downforce from the design itself, and this could be interesting while driving.
This will knock the mpg out of any vehicle.
How do you attach/detach? Seems you are stuck with this thing on the back for the entire trip. Or you have some weird clamshell that can fall over in wind if detached.
Access to the rear.
No galley.
It is a very expensive, badly designed bed, with a tent side. Buy a $50 tent, spend 5 minutes instead of 1, have more room, more convenience and more money to take on a trip.
I'm sure they sell them, but not to anyone I know.
Edit after reading more on their site - Weight is 275 lbs. Must remain attached to tow vehicle to use. Height is above a large SUV. Looks like it only uses a single hitch attachment point.
dave