Appropriate age group(s):
Preschool and Younger
Elementary School

Description of technique for dealing with temper tantrums:
Purchase one of those note pads that can attached to your windshield with a suction cup. The pads of paper are held by a plastic mini table as a writing surface. Attach the suction cup to the shopping cart (usually the plastic seat will do, there should be room between the child's legs) and your child has an instant coloring/doodle table to keep them busy while you shop.

Other suggestions or comments:
Attach the notepad in the middle of the seat so that it is facing your child.