So far as I know, there are exactly two shipping devices in the world that have USB-C: the new MacBook and the new Chromebook. I don't know the availability of parts and whatnot, but clearly this is the future of all things, it's just a matter of when. It never would have occurred to me that the business about "who powers whom" over a bidirectional cable like this is sufficiently confusing as to require user dialogs, but it all makes sense.

Edit: I forgot to mention the oddball Nokia N1 tablet and, just announced today, a new Asus tablet.

Minor digression: I was pondering the new MacBook as a replacement for my four-year-old MacBook Air (13"), but I initially rejected it due to the total absence of useful USB-C accessories. If/when the HydraDock comes out, that might be the thing that tips my hand. You can replace all the dumb dongles in your bag with one big dongle, not unlike the very original and much beloved Sony 505G. The same people are also working on a USB-C car charger and other such goodies. Of course, in a year or two they'll be overwhelmed by the generic Chinese brands, and you can rest assured that every damn one of them will get something important wrong. (Sigh.)