The design on this seems less than ideal, as I imagine the clear plastic door reduces the efficiency somewhat, and it's much more complicated and costly to make compared to a traditional Pot-in-pot design, which uses the same principle.
A more advanced version of this concept that could work in any humidity (the clay designs only function in dry, non-humid regions) was seemingly in development by a company called Coolar, but haven't updated anything since they released this presentation. But that design certainly wouldn't be within the grasp of the people who most need it, compared to the clay designs.
EDIT: After a bit more investigation, the upright fridge design by Mitt is indeed pretty lame. It can cool interior temperatures down by 8 degrees C compared to ambient, which is about 14 degrees Fahrenheit lower.
In comparison, the pot-in-pot 'Zeer' design can reduce internal temperatures by up to 22 Celsius, or 40 degrees Fahrenheit. So... I'm starting to think this upright 'fridge' is more of a novelty than it is practical.
So if you're curious about these, live in a climate where it is usable, and want to try building one, here's some instructions on building the Zeer design instead.