This year is not only the 30th anniversary of the *[Back to the Future](http://en.wikipedia.org/wiki/Back_to_the_Future)* franchise as a whole, but is also the year in which *[Back to the Future II](http://en.m.wikipedia.org/wiki/Back_to_the_Future_Part_II)* is set.

**Which technologies that exist in 2015 (at least as prototypes) were correctly predicted by *Back to the Future II*?**

[![Three people riding hoverboards in the film](https://i.stack.imgur.com/WUqnG.jpg)](https://i.stack.imgur.com/WUqnG.jpg)

To clarify, I am looking only for technologies that were not in existence at the time that *Back to the Future II* was made. (All technologies that appear in *Back to the Future II* are relevant, regardless of whether they also appear in other works.)