IoT systems perform continuous data processing in real-time, transforming data from sensors into final results and actions. Complex IoT systems may feature multiple devices, with different hardware and real-time operating systems, yet having a common programming language to model such data transformations is a desirable property: makes it easier to simulate a complex system and verify its soundness. The presentation demonstrates a programming environment well suited for such a purpose: the audience will see how it embodies the reactive computing paradigm, why that paradigm is ideal for IoT systems, and how it is amenable to a wide-spectrum of users.