Remember those bikes that didn’t have gears and handbreaks, and you had to pedal backwards to break? The backwheel of those bikes are perfect for a giraffe wheel. There is a peice from the wheel attached to the frame. When the wheel turned forward, this peice did nothing, when the wheel turned backwards, it would grip and stop the wheel from turning, thus breaking. Detach that peice and the wheel from the frame. Then take off that breaking peice. You will be left With a geared, uni-hubbed wheel. Perfect for a giraffe.
It’s called a “coaster brake”. This kind of hub has some play in it. You would be very sad when you had to do a quick little balance thing, and you had to turn the cranks a quarter turn before anything started happening down there at the wheel.
A skilled rider might be able to make it coast, though. Under certain conditions. . . .