I don't know of any smartphones that have a "keyboard" button alongside the other basic buttons (which are "home", "menu", "back" and "Google search" on my Rezound). By "keyboard button", I mean one that would bring up a keyboard to type on whenever the user wants.
This sort of button would allow you to avoid the (for me very frequent) situation where the cursor is *already* in a textbox, and yet you have no keyboard with which to type into it. This means that you have to painstakingly aim your finger at the textbox, and if you've already started typing something beforehand, you have to hit the exact spot where you wish to begin typing again.
Do any current smartphones have this feature? If not, why don't you think it's been incorporated into any designs thus far?