Here's an oddly interesting iPad "keyboard" option. Instead of adding an external keyboard, Tactus built an iPad mini case with a built-in screen protector that has key guides that rise up from the screen when you need them.
It's called Phorm and it uses invisible channels embedded in the screen protector to fill transparent pockets with fluid - which creates the key guides. Currently it is only available for the iPad mini and only works in portrait mode.
And you don't actually press the bubbles like keys, they're just there as "guides" – they appear near the top of the actual on-screen keys. There's a slider that raises the bubbles – it's completely manual: when you want the key guides, the slider fills the pockets with liquid, when you want it to go away, you slide it the other direction.
Honestly, it is way too pricey at its $150 pre-order price – you can get a $30 transparent keyboard overlay that actually works pretty well. I think this is really just their short-term "get something shipping" product.
As the technology evolves, I would expect some kind of tactile key feedback from Apple or Samsung to be built in to their devices (maybe using Tactus' technology.) I think they're just waiting for materials science to catch up with the idea-space.
Here's a clever marketing video for the technology: https://vimeo.com/43431035
In any case (pun intended) watch for more tactile feedback keyboards on consumer products - I think this is just a teaser.