It works with specific iPads loaded with a specific Adobe or Adobe compatible app. Quoted from their site:
Ink and Slide are designed to work with iPad 4+, iPad Air 1, iPad Mini, or iPad Mini with Retina display. (Note: There is a known, intermittent issue with the iPad Air 2, in which Ink stops drawing mid-stroke. After thorough investigation, we suspect the solution will require involvement from Apple, and we are trying to work with them to resolve the issue as quickly as possible.)
I'm always looking for ways to simplify my design sketch work flow. Right now I'm hardwired to my desk with a wacom cintiq which I love . But there is something really appealing to the untethered freedom this system can provide.
It's more than just a stylus, the aluminum bar to the left (in the picture) is what they call a "slide" and it lets you draw precise straight lines and curves if you need to.
As of this post the price is around $125 and fulfilled by adonit.
Certainly adding this to my wishlist!