There are fun things that indirectly improve typing that can be done on the iPad too (which can be used with the keyboard onscreen or an add-on keyboard).
Doublescoop lets kids type notes to grandparents or other trusted adults.
Scribblenauts requires keyboarding to enter the item you want to create, and then does a spell-check for you.
I'm using this as pre-keyboarding skills, just raising awareness of where the keys are and how typing works-- in hopes that when we go to build fluency, some basic sense of the keyboard will already be in place.
DeeDee