Tactus had just the one early prototype on hand, and it was an impressive sight. They've developed a way to add a layer on top of your standard touchscreen which, when enabled, adds a set of buttons to the otherwise flat screen. This layer consists of a network of channels which feed a new type of fluid to certain areas on the screen. When triggered, you'll see and feel clear buttons on top of the touchscreen, making this the first retractable touch feedback user interface.
The buttons can be enabled and disabled at the flick of a switch, and while in use they don't drain battery life. But there is some cost to enabling and disabling the buttons, of course. They feel much like any buttons on a mobile device, and while that description is vague it's also a positive. I've used devices with buttons that were more difficult to use (the Amazon K3, for example), so I'm pleased to say that this is far from the worst on the market.
Now, I've read The Verge report on this tech and I must disagree with some of the points. I thought the buttons provided enough feedback, and in any case the production model will likely improve on any shortcomings.
The button layer can still be felt and seen when deflated, but it wasn't a huge visual distraction and the layer didn't make the screen all that much more difficult to use. Keep in mind that this is a prototype; I think that when this gets into production the button layer is going to be much less obvious when not in use.
Right now the Tactus prototype is using segmented panel with predefined spaces to be inflated as buttons, but their long term plans include much finer control. They're hoping to achieve a panel that can match the resolution of the underlying tablet, and that would enable them to create buttons of any size on-demand.
It's not expected to be on devices until the second half of next year.
About the gallery: Several of the photos show a bare prototype unit. If you look at the face you can see the channels that the fluid will flow through. You cannot see the buttons because they would be formed by another layer on top of the one you see in the bare prototype. The screen assembly under that face is a run of the mill 7" screen/touchscreen component from Touch Revolution, one of Tactus' partners.