Create an ipad app for augmentative and alternative communication

I need to develop an iPad app which will be used as an aid for a handicapped person. It will work as follows: 1. It will have several groups of words and the words have to be scanned expecting the person to press a button. When the button is pressed, the selected word will be added to a command line. 2. This process has to be repeated until a sentence is formed. When the sentence is completed, a text to voice converter will read the sentence to help the person communicate verbally. (The converter has to work in English and Spanish) 3. The scan function is very important because it makes the app useful for the person. Instead of scanning word by word, it has to scan line by line first. When the line is selected, it will start scanning only the words in that line, until the desired word is selected. I need to receive the software working properly (probably after two or three versions) and the necessary documentation (program code, architecture). I have to be able to present it and modify it as simply as possible.