Two things for the nit-pickers out there: it's not actually invisible and, yes, the whole thing is just a promotional stunt in Germany, a way to highlight that the car, Daimler says, is "invisible" to the environment.
The way it works is that a camera on one side of the car broadcasts a live image to a multitude of LEDs plastered on the other side. So, when you look at the car, you see a representation of what's on the other side. It's similar to what some military research organizations are working on, but this is the first time we've heard of it used on a hydrogen fuel cell vehicle. Also, technically, the special F-Cell is only half "invisible," since the non-LED side of the car has the camera rig and associated wires. You can see how this works in the video after the jump.
A year ago, Herbert Kohler, Daimler's head of e-drive and future mobility, said he expects fuel cell vehicles to not cost any more than diesel hybrids by 2015. We expect he meant as long as they're not covered by LEDs, anyway.