What, exactly, is the point of this?
I mean, it combines the disadvantages of walking with the disadvantages of cycling.
If you're going to be bent forward, you should be riding a real bicycle with drop bars, or with flat/porteur/moustache/tourist/commuter bars set below your saddle height. If you want to walk, why should you have a frame slung over your shoulders if its only purpose is to connect two wheels that won't to help you move. And, finally, if you have a wheel in front of, and another behind you, you should have a pair of pedals or something to propel them.
I'm guessing the inventor of this device--called the Fliz--was playing a joke. On whom or what, I don't know. But it is funny to look at, so I guess his/her efforts weren't for naught.
Who says Germans don't know how to have fun?