With a single message area, the student could request "MORE" of a preferred item, food, or quick activity (such as bubbles, a spin in a chair, squeezes, etc.), and then move to two messages for with the addition of "ALL DONE" to refuse, protest, or escape non-preferred tasks. These same 1- to 2-message layouts could be used for highly motivating cloze activities ("E-I-E-I-O" if Old McDonanld is motivating, activating the on screen "button" to fill-in his name during a group song or rhyme, etc.) or Hi / Bye if greetings are motivating to your student. Here are some screenshots of these three, free apps:
(field of 1-12 message areas/"buttons")
(1, 4, 9, 16, or 25 message areas)
(field of 4 or 16 message areas)
Single button for cloze Old McDonald activity.
Image drawn and saved in the Doodle Buddy app & "Select from Library" in PicCardMaker