Refining the QWERTY keyboard for one-handed use, ZenNotes is a text editor geared towards writing that allows you to type in comfort for a long time, not hunt and peck, while you relax or hold your iPad. Regardless of your typing method, you may find the ZenNotes keypad more compact to use than the QWERTY keyboard.
The FREE version allows you to listen to background music and manage ZenNotes documents on your iPad. The full version, available at https://itunes.apple.com/us/app/zennotes/id539563746?ls=1&mt=8, adds e-mail, print and file sharing capabilities.
The ZenNotes keypad, also known as the TREWQ (pronounced "true-q") keypad, collapses the three rows of the QWERTY keyboard into six rows so that you can touch type using one hand. The key corresponding to the same finger on the other hand is located directly above, taking advantage of your existing touch typing muscle memory.
For full details, see the ZenNotes User Guide at zennotes.ca/userguide.html