In this paper we describe the material of a construction kit designed to allow children to build their own handheld and wearable devices to meet their interests and passions. Children don’t work with these machines, they learn, play and grow with them. Informed by the types of projects that children have done with this material in the context of educational research in science and engineering, we present a few scenarios for why children would build their own handheld or wearable computational devices. We believe that these application scenarios and their appeal to children are strong evidence for why we should rethink the design of computational devices, particularly for children.