Here is one idea that I found that kept them on task. Students worked with a partner or two using our jumbo magnetic numbers (flashcards will work just as well) and went around the room creating sets to match each number using objects they found in the classroom. As evidence, they had to take a picture of their sets and include the number in the picture.
Once the students finished their number sets, I let them exchange iPads with another group to share their number set pictures and check to see that the other group had the correct number of objects in their pictures.
How have you used iPads in the classroom?