ProtoPie is a code-free interaction prototyping tool for digital products. Designers can explore design solutions with prototypes. After prototyping, ProtoPie generates a programming reference document for engineers, consisting of parameters and values for movements and interactions. This allows designers to reduce communication costs and engineers to implement original interactive designs precisely and without misunderstandings. Moreover, ProtoPie can utilize smartphone sensors. This allows designers to see a big picture of the system used by multiple users, and to design a complex service across devices such as IoT and connected cars.