Reactive applications is a wide class of software that responds to user input, network messages, and other events. Recent research on reactive languages successfully addresses the drawbacks of the Observer pattern – the traditional way reactive applications are implemented in the object-oriented setting – by introducing time-changing values and other ad-hoc programming abstractions.However, those approaches are limited to local settings, but most applications are distributed. We highlight the research challenges of distributed reactive programming and present a research roadmap. We argue that distributed reactive programming not only moves reactive languages to the distributed setting, but is a promising concept for middleware and distributed systems design.