This paper explores how a young child (56 m) builds an understanding of the cardinality principle through communicative, touchscreen-based activities involving talk, gesture and body engagement working via multimodal, touchscreen interface using contemporary mobile technology. Drawing upon Nemirovsky's perceptuomotor integration theoretical lens and other foundational aspects of Husserlian phenomenology, we present an in-depth case study of a preschool child developing mathematical expertise and tool fluency using an iPad application called "TouchCounts" to operate with cardinal numbers. Overall, this study demonstrates that the one-on-one multimodal touch, sight and auditory feedback via a touchscreen device can serve to assist in a child's development of cardinality.