onscreen keyboard behavior like on facebook

[onechipshot]

The onscreen keyboard within Facebook allows the user to move their finger accross the keys (key hit is displayed during movement) selecting the last key touched. This behavior is special fo my daughter who has CP. She is a very bright 13 year old. However, her fine motor skills are challenged. This method of selecting what she wants to type really works for her.

How can this behavior be applied to other Ipad aps like notepad and email applications. Thank you.