Laptopmag recently has reviewed this new device from REDFLY that is the inheritor of the Folio legacy!
Intomobile.com have a page with demo video that gives a good overview.
I've covered the rapid rise and fall of the Palm FOLIO here in previous posts, but it seems people are willing to have another attempt at breaking the limitations of mobile phone input (keyboard) and output (display).....brave people, well done!
As demoed, its a great improvement for input and viewing for applications in Windows Mobile devices with small screens, especially when the applications are smart enough to take advantage of it.
However, I still have reservations about taking along a significantly sized device (plus its power adapter) that is useless on its own without being connected to the mobile phone.
My proposal all along has been to have a collections of devices that are all useful in their own right.
So, I would propose that the viewing part of this functionality be made available when the mobile phone is connected to an eBook Reader. The mobile phone is useful and highly portable on its own, the eBook is great for reading and has a long battery life on it's own, and when you put the two together you get something new beyond the capabilities of any one piece.
Keyboards remain an issue that needs work. If it wasn't for the lack of haptic feedback from touchscreens then we could go the way of the proposed OLPC XO 2 - but I'm not sure I'd get proficient at typing on a hard surface with no moving keys, nor if I'd like it.