Alternate keyboards have fascinated me ever since I first got a smartphone capable of using them. My most memorable experimental trials were 8pen[1] and one where the user would "slalom" from key to key as columns of letters would move from the right side of the screen to the left, expanding the target area in a fisheye type zoom as you neared your desired letter.
Unfortunately the name of the second keyboard evades me, but as a single-finger input it was fairly efficient, and I believe targeted at disabled people with limited mobility.