Hi there.
I am a developer of this keyboard, and if you have any questions to ask I will be happy to answer.
The goal of the project is to create a really optimal mobile keyboard. It must be pocket-sized but easy to hold, fast to type, and not too hard to learn.
And none of current physical solutions feature this set of features.
It's good for learning back-typing when you don't need to move your fingers between several input elements, that's why there are only eight input elements on the backside. They are four-way, because more directions are hard to operate fast. By this exact QWERTY mapping is not possible for this device. Nevertheless you can set any layout you like to try to reach more familiar feel of typing. New layouts are constructed simple by modifying xml-config on the phone side.
QWERTY makes sense when you are creating a device for those who can already touch-type on QWERTY. For those who are migrating from touch-screens it is better to create layout which is optimal for this new kind of device.
Concerning current size (it's 128x70x10mm about size of a smartphone) - we also have clip-case prototypes which add only 4mm of thickness to the phone, like this
https://www.dropbox.com/s/sjo9wjcxbc8o45c/iphone5-collage.jpg?dl=1.
But we start with universal model to reach maximum early adopters.