The Hendo hoverboard came out some time last year. It might not be just like the one in Back to the Future II, but at least Tony Hawk rode it. Also, it seems Hawk is helping with the next version of the hoverboard.
How does it work? The Hendo engine uses electromagnets that produce changing magnetic fields to interact with a conducting surface. Basically when these electromagnets change the magnetic field that produces an electric current in the metallic surface underneath the hoverboard. This electric current then produces its own magnetic field to repel the hoverboard electromagnets. Although the idea seems straightforward, it’s difficult to get it to work in real life.
Why is it awesome? It’s clearly a skateboard that hovers. That’s pretty awesome.
Where does it fall short? The primary problem with this hoverboard is that it only hovers over a conducting surface. If you put this over water, the electromagnets would still make changing magnetic fields but without an electric conductor below it there would be no repulsion. The other small problem is that it doesn’t ride like a skateboard. Hopefully this can change with the help of Tony Hawk.