Might want to check and see if the pedal are directly connected to the wheel, in other words, does one front wheel revolution = one pedal revolution. If the pedals won't ratchet (=pedals and feet can be held stationary while the bike rolls), you'll be severely limited in speed and then, if you're going downhill, your feet could fly off.
But with something like this that's designed for adults, I would have to assume that the pedals ractchet?
There are so many inventions, I would check and see if this one is just the newest gimmick or if it really offers the most "bang for the buck."
Why not training wheels on an existing bike, for example?