Amidst rumors Microsoft is developing a one-handed keyboard, the Thumbly iPhone keyboard app is an excellent example of how such a design would work. It is made for the way you would naturally hold your smartphone, with both left hand and right hand capabilities. The gesture-based controls use a swipe motion to help you perform functions like caps lock, delete, return and shift. The Thumbly Keyboard is also predictive, knowing what you are about to type before you finish. Autocorrect can also be disabled.
The one-handed iPhone keyboard would make smartphone use more efficient. Its ergonomic arrangement remedies the awkward way one would use a traditional keyboard with two thumbs. Instead, all keys cab be reached with one thumb.