Looks good. Basically a battery and keyboard with trackpad, really. Although I'd even more, like to have a slider case. I would pay hundreds for a good slider qerty case for Note 4. In fact I was thinking, i HATE onscreen soft keyboard and would miss my back ahd home button on a Note 8 if it's like the S8. But, a case like this would fix it! And screen would be big! Although the Flip Cover is also sweet. I still don't get why many are obsessed with getting rid of tactile buttons. Just for me, personally... Haptic is no replacement, Swype is actually kinda disappointing and I find its prediction crap. I miss my Droid 2 keyboard.
That said, if this is good quality I might buy. I never heard of Sentio but I will try it tomorrow with my phone and an office keyboard.
I was always fascinated with Padfone too as can be imagined. This seems like a better option since it can work with any phone.