Ran across this article, describes a key layout pattern called KALQ. Might be interesting for those building ultra-compact layout keyboards;
http://techbeat.com/2013/04/kalq-keyboard-layout-makes-typing-34-faster/"Dubbed KALQ, the layout was designed for mobile touchscreen devices by Germany’s Max Planck Institute for Informatics, in collaboration with the University of Saint Andrews in the UK. The layout was created based on computational optimization techniques applied to thumb movement patterns, resulting in a split keyboard that has 12 keys on the right and 16 on the left. The new design is called KALQ for the letters in the bottom row on the right side of the layout. The right side also includes all the vowels.
The new layout allows users to move both thumbs simultaneously: as one thumb is typing, the other is already moving towards its new target, which is ideal for a mobile device. This movement is not possible with the standard keyboard, which actually slows down thumb typing."
